Bullshit. You don't know anything about either the size or the TDP requirements of the next Xbox.
What evidence do you have to indicate the next xbox will be compact and/or have a low TDP? The original Xbox proved that MS doesn't mind releasing a large console in order to make it powerful.
GAF was damn right adamant that MS was going with AMD. Why would they have any more credibility in their guesses about how big the next Xbox will be?
you don't need evidence it just is! you cannot fit an incredibly powerful system in a games console style space without some serious thermal design like the PS3 had. and nowdays GPU's use even more electricity and produce even more heat than they did 7 years ago. luckily TDp has gone down on higher end CPU's (my q6600 has a TDP of 105w and the latest ivy bridge i5 has a TDP of 77w and its much more powerful)
but yeah GPU's use much much more power now. the GPU in the 360 (roughly a Radeon X1800) has a TDP of 70W and the ps3's (GeForce 7800 equivalent?) has a TDP of 81W
Modern high end GPU's have a much higher TDP the GTX 670 for example (a high range card) has a TDP of 170W! The AMD Radeon HD 7870 also has a TDP of 175W.
Neither of these are each companies best card and the top end cards use much more power and produce even more heat!(not including dual chip cards)
The GTX 680 has a TDP of 195W
and the HD 7970 has a TDP of 250W!
Putting these chips in a confined space will be a hefty challenge!
I know being bleeding edge is Microsoft and Sony's thing. im just saying they very well might not be the most powerful machines on the market, but they could have very respectable parts.
Saying that, I hope MS and Sony Rise to the challenge and succeed.