Honestly, I think depending on how the next 2 years go, that could be up to Boller. If he plays in McNair's absense well and shows he'd learned how to be effective, then other teams are going to want him. Remember there are some guys that are going to be retiring at some point. I could see a scenerio where Boller goes to Kansas City to fight for the starting job since Trent Green is getting up there in years and without looking it up I can't even remember who their backup is. And KC has a killer offensive line.
Boller's contract ends before that, and I can't see us extending it.