^ Renner looks set to be a busy boy, doesn't he? He's taken over the Bourne series, there's Hawkeye in the Avengers and I think that the studio envisage Hansel and Gretel being a franchise too.
All the more reason that the people who wrote his M:I contract might've included a clause committing him to sequels, especially if they signed him in the first place with the intention of making him the new lead. Actors who sign up for franchise films these days are rarely signed for just one at a time. The contracts specifically commit them to multiple films, especially if they're busy, in-demand actors whose availability needs to be guaranteed in advance.
Ahh, here we go:
Do you have a contract for another one?
Yeah. If they so choose to use that. Or they can tell me to piss off. You know what I mean? It's their call. Like any other franchise, you want to keep the possibilities open.
So if they want to bring him back for M:I 5, he's already contractually bound to appear. Although if they don't want him back for whatever reason, they'd just let him out of the contract. But as you say, he's a popular fellow right now, so they probably would want him back.