I agree that Belfort moving to train with Couture is interesting as Couture is a solid game-planner, but there is one key point to consider here:
Sonnen is considered by many to have the best pure MMA wrestling. In the world. Typically mentioned in the same breath with GSP and his Sonnen's Quest teammate, Dan Henderson... and iirc, I believe Henderson has even stated that Chael has the best wrestling in mma, and that's a pretty serious co-sign.
So I'm not sure we'll see Belfort storming in with a Sonnen-like fury and thrashing the Spider on his backside.
Though you raise a good point in that Belfort's striking acumen (much greater than Sonnen's) does add another dimension to the equation.