Microsoft will- they simply have the biggest E3 news, probably price cut and 360-slim version. Sony probably won't cut the price at the E3 but might want to wait a bit and see what effect the 360's price cut will have. And anytime you have news of a price cut, it's a big thing. Natal will be the icing on the cake and since MS has done a lot of moneyhatting, they have gotten close to 85% of developers working on Natal, so I'd imagine quite simply that the number of offerings that Natal has will dwarf the PS3 Move's titles even when the Move will probably beat Natal with respect to quality.
Nintendo doesn't have any new gimmicks besides games, and Sony's move wont be as big as Natal, its PSN upgrade if it is happening won't have as much of an impact as MS's expect price cut and slim version.
However, I still stand by my prediction that the 360 size cut won't be as significant as the PS3 to slim was, as the 360 is already as big as the PS3 slim is now, where the PS3 was originally a lot bigger. Also, Sony will eventually counter with their own cut.
