The lead will be bigger than ever at the end of 2008, and it will probably keep growing for at least a few months in 2009.
I don't think Sony will cut the price early in 2009, but even if they do, in the best case they'll only have a few months to decrease the gap before Microsoft slaps another price cut on the 360 (if they feel they need to). Other than price, there's little that Sony can do to diminish the gap as basically all third party exclusives have slipped through their fingers.
In conclusion, by the time the next-gen consoles are launched Sony's best case is to be a few million away from the 360. If we're extremely generous, we can say they might be about tied (not something I'd put my money on). In the worst case, the 360 will have a bigger lead than they have managed to keep until now.
My Mario Kart Wii friend code: 2707-1866-0957
