In an interview with Sherdog radio, Firas Zahabi, UFC Welterweight Champion Georges St-Pierre's head trainer, said a move to 155 was more likely than a move to 185 for the French-Canadian superstar.
Now granted, this is simply speculative. Zahabi also mentioned that a move to 155 is far less likely with Frankie Edgar holding the belt.
The reason being is that both GSP and Edgar train Brazilian jiu jitsu under Renzo Gracie, so obviously these two have trained with each other on many occasions and would like to avoid each other in the Octagon if possible.
So, while fully acknowledging the fact that this fight may very well never happen, here are four reasons why Georges "Rush" St-Pierre would definitively defeat Frankie "The Answer" Edgar.