I think at the very least, the Avengers roster in Avengers 2 will now include Ant-Man, and possibly Wasp depending on the direction the Ant-Man movie goes (I said before they don't have to give Wasp superpowers if she's in the Ant-Man film, she can just be Janet).
It's only 1-2 more, not a big deal. Now, Avengers 3, after Phase 3, that might be different. I imagine Black Panther, Doctor Strange and others will be around in time for Avengers 3. I can't see Strange or Panther appearing in an Avengers film without a solo film first (whereas Hawkeye and Black Widow work on the team without a solo film needed). And come on, wouldn't you want to see your cinematic introduction to Doctor Strange being a full on cosmic fantasy film facing off against Dormammu?
But that's years and years away, so no need to worry about it now. I just hope they keep the level of planning and detail at the high level Phase 1 got. Between the solo films, the Avengers film, the short films and the comic tie ins, the MCU has had strong continuity so far, I hope that continues.