That's a bold prediction. There is a decent chance MS could win next gen, but outselling both Nintendo and Sony? I'm just not sure about that.
People think MS will continue to just focus mainly on their top exclusives( Halo, Gears, Fable, Forza) going into next gen, and not much else. If people haven't noticed, MS have been creating and acquiring studios left and right in the last few year. Right now, MS has the most in-house 1st party developers and we will start to see what most of those studios are making within the next year or two. Lets say, half are creating Kinect games and mobile/arcade games, that still leaves 10 or so studios creating "core" IP's.