What if they plan on making Ant Man an infinitely more interesting character by exploring his explorations of the infinite and adding more scale to his character by giving him an important role over multiple dimensions like the negative zone? Bringing all of the creation of the super villain prisons stuff to the big screen. And even exploring possibilities around alternate timelines, further exploring other dimensions with a team of Pyms & confining a lot of that type of stuff to Ant Man's character/team. Emphasizing his role as a scientist on the leading edge of world changing technology.
What if the recent rumor about both Adam Warlock and Magus being in GoTG is true? Could there have been an apparent time paradox, creating an alternate version of a character, and a great disturbance in the timeline?
The "universal truth" that Selvig can now see after the cube's power showed him so much "truth" about the nature of the universe. The "truth" known to the Universal Church of the Truth: that there isn't only one universe, but an infinite number... a multi-verse.
However, this timeline needs to be a certain way and Ant Man has to work to maintain that (meaning the time-travel elements don't really affect the other movies as much... or at all like in Iron Man 3 or anything occurring before Avengers 2, minus Ant Man)
What if both Pym and an alternate version of himself end up being in this film--as well as Lang and Janet?
We end up getting Young Pym from the 60's, an older astrophysicist Pym who abandoned microbiology, Janet from the 60's, and Lang from the present--all working together. They can run into other versions/incarnations of Ant Man along the way, and each take on different personas when they all come together.
Pym and Janet end up time-traveling to the present from the past (from the 60's directly to Avengers 2). A recast Red Skull could reappear from the past as well, and Cap has a new out of time soldier friend to bond with in some ways. A mysterious being takes great interest in the double of Pym created at the end of his movie and takes him and the alternate Jan across time and space to the future where it is explained they will be needed, and nothing more. So they don't meet Lang or Old Pym/Selvig until the very end of the movie. But they're traveling from an alternate past, or what could be considered a time loop, that Kang successfully takes the Ultron technology from. Like with Kang, there ends up being a "double" of Pym that travels to the present time-line. This would then be tied to Magus/Adam Warlock and some of the forces at work in the multi-verse.
Selvig reveals that Janet died in his past, which is partially why he never stayed Ant Man in the current timeline.... But now we have 3 Ant men (one will inevitably become Giant man, and Old Pym/Selvig invents new technologies for Shield). With Janet as the leader to the correction of the multi-verse...
And what seems to be a time paradox has occurred at some point in the past and future, causing GoTG to partially focus around the 21st, 22nd and the 31st centuries.
What if the 60's Pym stuff and having Lang in the present is all because Kang, his alternate versions, and Ultron have ended up being tied to the Magus/Adam Warlock phenomenon? As well as Kang's problems with Thanos in the future... Kang knows which timeline Thanos can be stopped in... if he can... and this affects Kang's vision of the 31st century + what the Guardians are up to there. The young ant man unexpectedly shows up from another time and helps Lang defeat Ultron in Avengers 2, & could have a bearing on the overall outcome of the series. Someone who wants to save the universe from Thanos knows that Ant Man has to be in that battle in Avengers 2... Even if it takes a little time manipulation, and a loose end Kang leaves behind to get Ant Man there.
This means he could randomly show up by way of time travel in Avengers 2 before we find out what happened fully in Ant Man... Ensuring that Ant Man and Ultron will be in Avengers 2, but saving their full story for later because of Kang's inclusion/manipulations-- being able to explain their sudden appearance. "Selvig" could help here too.
Selvig was already looking into wormholes, but he never considered the possibility of parallel universes... alternate timelines, effects on the timeline in the past that have not been uncovered yet or altered events that changed the course of Pym's life.. rewrote his timeline like some of the "Pharaohs of old". Causing him to look into wormholes. Exploring different dimensions, like the negative zone, or dimensions of a different scale. The truth the cube showed him opens him up to the alternate paths he could have taken and those that have been created... i.e. Whichever superhero name he wanted to stick with. Or just sticking with what he had started when he invented Pym particles and the Ultron prototype in the 60's. Shield spooked him away, tried to give him infinity serum as they did BW and when he didn't want to play hero anymore they confiscated all his stuff. "Pym" was never heard from again and he became Selvig.
Meaning the Pym from the 60's could converge with a Pym/Selvig in the present. As well as Lang who now has the technology after Shield handed it off to him.
Essentially what I'm strongly, and obviously suggesting would be a huge reveal that Selvig has actually been Pym operating under a false name this entire time-- an extension of his changing identity thing in a different way. This Pym rejected the life of a hero and Selvig is the result. In the past the incident that scares him away from Ant Man/Shield also creates the time-loop in the 60's & the alternate version who travels to the future. So all is not lost, and it was really Kang's doing. messing with the timeline. Meaning the 60's may need to be revisited again in an Ant Man sequel back to the future part II style. Because Kang will return to this point to keep reacquiring Ultron...
Taking on a new identity or having multiple incarnations isn't really completely new for Pym. In Thor he would then be referring to the man he once was, before Shield took his stuff and passed it off to Lang. It's like the "I have a friend story"... I think this is why he originally says "Pym" in the early drafts, a way to honor his old personality...
The way the timeline has gone resulted in Pym running away from the life of a hero and becoming Selvig.
Young pym being brought into Kang/Ultron's timeloop not only changed Pym's life, it also created the double by accident. Which partially undoes Kang's plans. Old Pym now has a chance to stop a new version of Ultron with the help of his younger self when Kang sends Ultron, Red Skull and the masters of evil from all across time and space to give each of the Avengers, and the Pyms, a personal battle in Avengers 2. Personal enemies that seem to come out of nowhere. Really it's Kang assembling the masters and Ultron, then sending them from all across time and space. In a desperate move to control the future while Thanos ends up waking up to Kang's plans.
Ant Man shows us the story of what became of Pym in the 60's, however the creation of Ultron leads to Kang's involvement...
This links Pym and Ultron to the alternate versions of Kang, and to the Magus/Warlock as well as other disturbances to the timeline in general. Making the Pym team: Selvig, Young Pym, Lang, Janet and any additional variations on Ant Man, defenders of the multi-verse, micro-verse, and all dimensions. In the Ant Man movies they would basically work together, journeying to other times and dimensions to stop Kang's manipulation of the timeline. A time loop is inadvertently created by Kang while Pym is developing his powers. Resulting in two versions of Pym and Two versions of Ultron...
One Ultron is defeated by the two Pyms that come about by the end of Ant Man. One Pym survives to change his identity and becomes Selvig after Shield's reaction to this incident. At the end it's revealed Fury always knew he was Selvig and chose not to chase him or scare him when they brought him back in after all these years. This changes Selvig's apprehension about being back with Shield at the end of Thor slightly.
Lang has been brought in recently in the present but only uses the technology and could want to steal it for AIM.
The other Pym who Kang inadvertently creates will be his undoing, and is secretly whisked away by a mysterious being who promises to take this Pym to a time and place where he is needed for the future of the multi-verse. Young Pym from the 60's is carried across time to Avengers 2 where he meets himself (Selvig) and Lang for the first time.
From there they put their heads together to figure out the Ultron problem, time-travel for the good guys (to maintain the timeline against Kang's attacks, something done in Avengers 2 any possible Ant Man sequels), the key to the negative zone and anything to do with the containment of very powerful villains for Shield..