Has he really been beyond expectations? His numbers are pretty much in line with what he did in 2009 and 2010. I was always willing to give him a pass on 2011, because having had mono myself I know just how badly that disease will kick your butt. I was surprised he pitched as well as he did last year. What he's done this year is pretty much who he is, and I'd imagine he'll be able to do it for a couple more years.
That said, it's simply too early to worry about extending him.