> I suggest PowerEN because it's the only 16 core PPC I know of, but
> then I remembered the Blue Gene chips have 16 cores now as well. Both
> use the A2 core which sounds remarkably similar to the PPC core used
> in the 360 and Cell.

Well, it could as well be a yet undisclosed chip different from PowerEN or Power BQC, but still be compound of 16 A2 cores. Or it could be a chip compound of 16 cores that are not A2 and which may be containing VMX128-compatible execution units, thus even be a sample chip of what's supposed to be used in the finalized console hardware.
If we take this current rumour serious, I guess the public information available (16 Power Architecture cores) is still much too sparse to hazard any educated guess of substance.