Changing the roster for Avengers 2?

[Sneakronicity]

Why do we have to change the roster? The first Avengers was about assembling that particular team, and I personally want to see them really work together, both professionally and personally. They were only a team for the end of the movie so it would be a bit of a disservice taking any of them away for the second film. Adding another character in could work but I don't want to lose any.

I would also love to see Hawkeye get more development because he got the shaft majorly in the films so far (which doesn't bode well, but I have hope!). I also like spideymouse's idea of possibly splitting the team which could allow for more development in smaller groups.