Originally Posted by Raiden
The way I see it is that the MCU as it currently constructed does not really permit Pym to be a central character. If Ultron is to be in the MCU it needs to have some connection to one of the main heroes of the Avengers, such as Tony Stark, and to suddenly introduce Dr. Pym and expect him to have such a pivotal role in the Ultron saga would not have made sense. I know that it goes against the comics lore, but I think by not having an Ant Man movie before Phase II (and Edgar Wright opting to use Lang instead of Pym) pretty much sealed the fate, since Thanos was never going to appear in Avengers 2 due to his importance and power level in the Marvel Universe.
However, if there is anyone I'd trust to do Ultron justice sans Pym, it'd be the writer of Astonishing X-Men, Joss Whedon. I believe that in the end, he will make a movie that even the Ultron purists would like, and we should not judge the product before we see it.
It's not even that we're Ultron purists. We just want to see justice done to Ultron and Hank and one without the other is not justice.
I just hope Whedon remembers his own words (your sig).