Re: Changing the roster for Avengers 2?
The only way we get Spider-Man (or X-Men, FF, etc.) in the MCU is if Sony (or Fox for X-Men/FF) realizes that piggy-backing on the success of the MCU only works if your character is introduced into the MCU because people get excited at the possibilities of these characters co-existing on-screen at the same time.
Fox has realized this and that's why they're trying to build their own cinematic universe with X-Men and FF (which will fail miserably because those two franchises don't mix all that well by themselves, and because...well, you know...Fox).
I would imagine that Fox and/or Sony will eventually be willing to make a similar deal that Paramount made with Disney, which is..."Let us distribute the films for our licensed characters and you can produce the movies as you see fit". In this case, the characters are for all intents and purposes back at Marvel, which Fox and Sony still get to rake in plenty of cash from distribution.