That depends on if Marvel wants an Avengers 2. By that time Downey will want to move on(RECAST!)
Evans would probably be in
Jackson's tied to Marvel till he dies
Ruffalo would still be fairly fresh and still up for playing Banner
Renner in, unless a Hawkeye movie is in the works
Johansson is tied to Marvel for multiple films... unless she says something bad about them.
When she signed her contract it was widely reported how bad a deal she got.