I doubt it. He has stated many times that he is not a big WW, he has also stated that he is not used to cutting weight, and does not like doing it. I also doubt he is ever out of shape during the off season... so I'd be willing to bet he walks around at 185-187, like he says.
GSP is not like the typical fighter who has an off-season, then does a 8 week camp to get in shape, ya know?
First link after googling "Georges St Pierre weight:"
Also from same source:
02/08/2007 @ 02:36 PM
How about watching the 105 weigh in Q and A, he's said many times he's trying to gain weight for preperation to moving to MW, he's closer to 200 pounds now. To answer thread question, no GSP couldn't make 155 without killing himself.
HW: Junior Dos Santos
LHW: Gegard Mousasi
MW: Anderson Silva
WW: Georges St. Pierre
LW: Kenny Florian