I'm not a fanboy, i"m a fan of the sport and martial arts period.
I'm predicting a convincing win by GSP. You can't predict what he will do beside that he'll try to use the opponent's biggest weakness as a tool to win since GSP has practically no weakness. Wrestling, GNP, guard passing is what GSP usually uses to win fights, not because he wants to be boring or that he's one dimensional but that is usually the weakest link in his opponent (the wrestling).
I'm predicting, GSP keeps things upright for a while, gains confidence when Hendrick's punches don't land and win by TKO or Submission after strikes.
Condit was a more well rounded fighter and couldn't finish GSP when he had tons of ring Rust.
Condit Vs Hendricks was close and I liked how Condit Fared (at his punches, was active as hell from his back). If Hendricks tries to take GSP down (possible,hard), he won't do much damage from the bottom as was shown by the Condit fight (while GSP being light-years- ahead in BJJ).
Bottom line, Hendricks has a puncher's luck. He can totally win, but betting against the champion at his prime is usually a bad call.