Actually, I'm happy with this. My only fear for the Wii U is that the ingenious possibilities available with the Tablet would never be explored because no one but Nintendo would care about it, and Nintendo would offer a lot of "casual" stuff. If MS and/or Sony is also including a tablet, third parties can allow themselves to focus on taking advantage of it without limiting their sales to one platform.
But this does make me think - the Wii U tablet is rumoured to be a pretty advanced/expensive piece of kit. If MS are including a comparable device and a Kinect 2 as standard, how much power will they be able to pack, bearing in mind the importance of cost? I'd assume not enough to be well above the Wii U, which then makes me think they'd want to launch not long after it.
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Who knew the Rivalry Rumble would be so predictable? SuperNiceDog, that's who.