GSP is going to win by submission. The story is he's been spending a lot of time with the Danaher Death Squad which is currently leading the competitive jiu jitsu scene.
If you mean "leading" by winning matches under a certain rule set (sub only, no time limit or points), then yes. They have not dominated anything that had a ruleset that favored "classic" BJJ/MMA positions.
Their heavy focus on leg locks is very far from ideal for MMA though.
If you are not a roided brick house like Paul Harris, getting a leg lock is tough and leaves you open to a lot of face smashing.
Just think how good Rory looked in his attempts to get Thompsons legs:
http://imgur.com/OwDoG8D
ALSO
He and Firas have ALWAYS trained with Danaher and GSP could not even finish the arm bar on Hardy.