It'll be hard to not have a system more powerful than the current generation HD consoles in the next generation. Nintendo would almost have to be deliberately obtuse in order for that to happen.
For instance if they used GDDR5 and embedded frame-buffer, they could be lazy and only install 2 chips of 2Gbit GDDR5 to yield 512MB of RAM and 50 GB/S bandwidth from 2011 onwards as an example and still vastly exceed the memory performance of current generation systems with a Wii-like memory architecture.
Then they can take a relatively cheap 4-6* Blu Ray or equivalent drive, a smattering of flash memory and perhaps an off the shelf Fusion variant from AMD and they have a quick and nasty console slapped together which magically outperforms current generation consoles similar to how the Wii outperforms last generation consoles for a really low price.
Finally slap on $100 mark up and they can be done with it.
Oh forgot: ?????
Then PROFIT!
