I think that's too far to look down the road. It depends on way too many factors, Chapman for one.
Regardless, I will say I was skeptical about the extension (though supportive of the reasoning for doing it) but he has absolutely been worth it these last two seasons. He's made a believer out of me and I'm glad he's going to be a part of the Reds' playoff rotation.
"No matter how good you are, you're going to lose one-third of your games. No matter how bad you are you're going to win one-third of your games. It's the other third that makes the difference." ~Tommy Lasorda