The XBox brand is strongest in America because its by an American company as well as a highly recognized one.
As for your prediction about next Gen I disagree completely...before this Gen the Playstation brand was very strong in America but seems to have faded because of the XBox brand. With that said while the Playstation brand slowed in America the DS and Wii brands gained huge popularity in America and just like how the 3DS has the name DS in it I expect Nintendo's next console to have the name Wii contained in it.
I personally think that the P.S brand faded here because the 360 and PS3 are so similar and the 360 is made in America so people pick the 360 over the PS3 here.
Anyway, nobody knows what next Gen has in store for all consoles though I expect Nintendo to stay fairly popular next Gen in the same way that PS2 was successful partly due to the PS1.
