I doubt the next Microsoft console will even use an IBM based processor to be honest, aside from the extremely high end server stuff, and Cell (which they almost certainly wouldn't use because of its connections with Sony), their PowerPC based cores are out of date compared to modern CPUs from Intel and AMD. Actually I could imagine them getting Intel to make them a custom core with a couple of standard X86 cores and say 16 Larrabee style cores.
Also, RAM amounts in console generations are typically huge increases, much more than double as suggested in this article. The 360 for example has 512MB, the Xbox before it had 64MB (both systems have a shared memory subsystem). That's eight times as much. Given the price of RAM these days, I dare say 4GB is a very likely figure for the next Xbox.