I'd say he still has a ton of potential and just got introduced to the upper echelon of the division.
Not the first contender Fitch derailed.....likely not the last. Gas tank could use a little work; but Fitch is not a cardio friendly match up for anyone. (Not that GSP is...)
Give him a few more fights before you disregard him a future champ. 28 is not too old to improve.
Anderson Silva vs. Jon Jones is the best match-up the UFC has ever been able to arrange. Here's to hoping it goes down.