Originally Posted by cherokeesam
At this point, I personally believe the roster won't expand too much in Avengers 2, either; but I still see enormous potential if some of the Phase II movies contain more secrets than have been divulged so far. In particular, I'm closely watching the rumormill for the possibility of Ms. Marvel (and Mar-Vell himself, by extension) in GOTG; the possibility of a Dr. Strange cameo in Thor TDW; and maybe even early appearances of Pym and his entourage, if Wright is in the middle of/through with filming by the time Joss starts lensing TA2.
But that's all strictly wishin' and hopin' for now. I think what we've seen of Phase II so far indicates that the general theme is about the individual heroes now reacting to this brave new world they've entered. Phase I brought them all together; Phase II is about them exploring what it all means, and how they can use their powers to beef up against even larger threats.
I think added memebers in Avenger2 will be Hank/Janet (maybe just hank, or both) and Falcon in some capacity. maybe they all won't fight though idk. And then theres always the possibility of the GotG crew teaming up with the Avengers crew, but I'm guessing they save that for A3. I could also see Hulk in a minor role since he might not pop up in these next few movies but I really hope not.
But a Pym has gotta be there, for both future storyline purposes that will probably be implemented in this phase, and to gather hype for their movie. One stealing the show scene for Hank like the Hulk scenes in Avengers will gather probably needed hype.
so possible expansion of maybe 2 members at most I would guess.