Re: Changing the roster for Avengers 2?
I don't think they're worried about them falling off the pop culture radar. They're probably looking to recast a good amount of them after A3 though. No way Evans is returning, that's the extent to which I see RDJ staying as Iron Man, and it's doubtful that Hemsworth and ScarJo return either. Sam Jackson's contract ends at A3 as well, but he's such a team player for this kind of stuff, I can see him resigning for more films.
So they'll possibly be replacing 6 members of the original cast after A3 (2018).
2014 - Captain America: The Winter Soldier | The Amazing Spider-Man 2 | X-Men: Days of Future Past | Guardians of the Galaxy
2015 - The Avengers: Age of Ultron | The Fantastic Four | Ant-Man
2016 - Batman vs. Superman | X-Men: Apocalypse | The Amazing Spider-Man 3
TV - Arrow | The Flash | Gotham | Constantine | The Avenger | Hourman | iZOMBIE
TV - Agents of S.H.I.E.L.D. | Agent Carter | Daredevil | Luke Cage | Iron Fist | Jessica Jones | The Defenders