WELL, the fight is next week so, so much for saddest day ever :-p
Well, at age 32 he seems to feel that it would be time to settle down and have kids, etc. Also, a chance to retire and not be broken down physically by overstaying his welcome. Maybe start an MMA school. Also, he wants to give a chance to Rory MacDonald to get the title, and he wouldn't fight him because they are friends and GSP would probably become his trainer.
His trainer Midoux said that. It's on RDS.
I'm thinking this is part reality, part pressure on the UFC to raise the ante for a potential Silva VS GSP fight. GSP is not stupid: fighting Silva is a tremendous risk and if I were him, I would bleed the UFC for as much as I can of guaranteed money to do it.