I think he will likely be long reliever. If they clinch early, he could be a 6th starter which could be used to setup the playoff rotation.
The only one I could see being removed from the rotation would be Hutchinson, but that is only if he reverted back to his woeful ways on the road. I could also see him getting a spot start for Buehrle since he's mentioned that he's "grinding it through" the past few games. I would give him a break if possible (just not enough so it affects his chances for 200+ innings again).
It's weird. I remember how much he wanted out of Toronto when he first came (due to the dog banning), but now he seems to love it here. And that is before they had their recent success. Even last year, he seemed like a different person (when interviewed, for example). I also think the banning has been removed, so now that he can have his dogs in Ontario with him, he'll be even happier.
I also think that, win or lose this year, they should re-sign him for a couple more years. He's been steady for them, and he brings a good veteran presence in the locker room.