When will Anderson silva and gsp fight?

As of now, Never.

A super-fight between Anderson Silva and Georges St-Pierre has been making rounds for the past couple of years. Silva is the current Middleweight Champ and GSP is the Welterweight Champ. So, in order for a fight to happen, both of them have to agree upon a weight to fight in and hence the fight could take a long time before it actually happens.