I believe they could still keep the big three (RDJ, Evans and Hemsworth) around past Infinity War. I'd also think another final "solo" movie for each of them is not impossible, and then afterwards have them in much more reduced roles. It seems to me, just from interviews and everything, that they love Marvel and the characters/stories and would be willing to create new contracts etc..
It's what I hope at least, I'm not a fan of recasting.
Guardians of the Galaxy vol 3 is almost a given
Spider-Man 2 is probably being banked on
A Black Panther sequel is very likely
Dr Strange sequel is also very likely
A third Ant-Man movie...depends on the second ones success..
A second Captain Marvel movie could come later in the phase...
On the t.v side....
I can see Agents of Shield still going, but not with as many of the current/original cast. Think like a revolving door of characters you see in police/hospital shows. And there's always a whole host of storys they could do...
Netflix could merge Iron Fist, Luke Cage and Jessica Jones into one Heroes for Hire. Daredevil could probably still go for a few seasons. I think around phase IV we'd start getting Moonknight, Blade, Ghost Rider etc
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What would I really like to see?
A Daredevil/Spider-Man team up. It seems ridiculous to me that these two (and the other defenders) will be operating within Manhatten and not come across each other once. Kingpin could be the main villian, with a few superpowered henchmen. Netflix or movie, I'm not fussed...but it should happen.
Like Fixxxer said, If there is to be a female Thor, don't make her a female Thor. Lady Sif is right there. She's a hero, Asguardian, and Odin could grant her the power of Thor so she may wield the hammer. Genderbending roles is stupid and a cheap gimmick.
A Thunderbolts netflix series. Thunderbolt Ross recruits a bunch of villians/questionable people to form a team to take out threats before they get out of hand. Zemo, Crossbones, Punisher, Deathlok, Elektra, Nuke, Abomination, Blizzard etc are all potential members that have already been introduced so far in the universe with Boomerang, Shocker (If Marvel worked something out with Sony) Bullseye (After an appearance on Daredevil) Cyclone, Atlas and Moonstone being able to be introduced for the series.
Fantastic Four back. Yep, they should get them back for Phase IV....just one movie in the phase though and have them face off against a villian we haven't seen them fight before, like Annihilus...or even Namor and introduce Atlantis.
Doctor Doom OR Galactus being the big villian of the phase, with the Avengers and Fantastic Four coming together to defeat him. Doctor Doom could have more buildup....