I think it's more than likely and that there's a reason for a lack of more concrete details due to MS' lockdown on leaks. I just hope that the Yukon paper overview, with its explicit inclusion of the PPC Xenon chipset for BC, is a part of the final 'Box. Certainly, with plans like that in place so long ago, and MS owning that piece and working with AMD to integrate it for compatibility with the new graphics and memory subsystem parts, they could leverage it as a powerful co-processor when not engaged in BC use.
ok, this post made me tight in the pants