Stewart has had a phenomenal year, but at the end of the day you're still talking about a guy with 124 pro innings in less than fifty total appearances.
I don't like to lose a pitcher who profiles well for GABP, but while Zach has a very solid chance to be at least an okay reliever in the majors, I think it's very far from a sure thing that he's a starter. 14 starts does not a future ace make- and it's doubtful Stewart will be helping a major league club in 2010 as a starter. A reliever? Yes, very possibly. A starter? Not likely.
"Building for the future" hasn't worked for the last decade. I guess I'm willing to stop talking as much about "the future" and start talking about "now". It can't turn out much worse than the other way did.