Originally Posted by snipekill2445
There are a few reasons how we know they'll stay low end.
1. It needs to fit in the console
2. It needs to be affordable
3. It needs to run very cool, quiet and use little power.
Not necessarily, they can strike all kinds of deals for high-end HW from the manufacturer with tweaked specs. For example, when the 360 was released it contained the first ever GPGPU, utilizing general shaders as opposed to the traditional vertex and pixel shaders and the PS3 was based on a 7800 GTX which was, at it's INTENDED release date still top of the line.
They do put high-end hardware into the two power-oriented consoles and, as they are supposedly being developed now it's not unrealistic for them to be specced with somehting like a 7970 or 680 which would, by the time of their release, be produced on a smaller manufacturing node making them cheaper and more energy efficient.
Another thing to keep in mind is that, quite often, especially at the start of this gen, the hardware itself was very expensive and MS and Sony took losses on their sales so that they could spread their consoles to more of the market. If it weren't for the massive software revenue, at the time of release, those consoles would have been far more expensive.
EDIT: Just to add to that, the original Xbox was built on the GeForce 3 Ti500 card, which at the time of development was the high-end unit.