Re: Changing the roster for Avengers 2?
How could anyone want Hawkeye to leave before 1) you get any character development and 2) you get to see some awesome trick arrows?
Marvel has done a lot to push Hawkeye lately. He's also being included in the new Avengers TV show, he's not going anywhere.
The roster will be;
The same + Falcon (unless he dies in the Captain America movie at the hands of Winter Soldier).
Depending on Ant-Man, they may include Pym, but I'm not sure.
I expect Thanos to defeat the Guardians of the Galaxy as well, so I don't see them joining the fight.