Ms stands and falls with natal. if natal will move a couple of million Xbox360s additionaly then there will be a gap. But if natal is just a mediocre success there is no chance for the Xbox to win the second place this gen.
I also see that Gem could be as big (or small) as natal after all ot could be a funny gimick and could improve fps on PS3 and the Ps3 would benefit before Natal even launches the next year decides everything. Its the final round. Then Sony and MS have no ammunition anymore.
I am confident that the Gap will be closed until 1.1.2011 ofcourse there are some unknown factors mainly Natal and Gem (also FFXIV). So everything can happen but If someone would force me to bet my money I would bet on Sony.