Cache-coherent Hypertransport is not part of the open standard. Until recently, I don't think AMD let anybody use that.
With Torrenza, AMD is letting coprocessors use it, but not full CPUs.
I suppose in theory that Nvidia might get away with a CPU in a single-socket configuration, but the other concerns would persist. I don't know if Nvidia has the license for x86, or whether Intel will grant it.
Even with that, it is unlikely Nvidia can produce a chip that would be able to match AMD on performance or price/performance.
Nvidia would possibly be something like a bargain-basement Transmeta, assuming that AMD doesn't control the use of its sockets. If AMD can control that, then it's a no-go for drop-in replacement.
The determining factor is what AMD (the cpu side) segments its offerings into, not what metric we think up.
An Athlon FX-60 burns way more power than a Sempron that will probably achieve 80% of the performance, but the Sempron is considered lower-end.
The high-end is basically made up of those processors that clock high and get high performance. There is a low-power segment, but it is not the same as AMD's high-end.
I'd be wary of putting too much trust in marketing, it's usually ahead of itself even when it's behind everything else. It's also waaayyyy too early to be spouting off numbers when they don't even have silicon that will instantly catch on fire if it's as fast as that.
I'd be impressed if they think they can clock a GPU that high, even more so if they think they can get something as broad as a top-end GPU that high. I don't think they can, but I'd be impressed with their enthusiasm.
Failing that, how would they feed 48 GPU pipes at 3GHz on a socketed memory interface that will likely supply less bandwidth than today's mid-end GPUs with half or fewer pipes and half or fewer MHz?
But if u think as Intel's Terascale having 80 cores at 3.1 ghz and giving 1 teraflop while maintaining reasonable power consumption, and AMD's on chip GPU running at 3 ghz with 48 GPU pipes while delivering 1 TFLOP. You can make an observation that this is feasible