Engineering samples of the Denebs only overclock to about 3.6 GHz so far, at least from what I have seen. That will probably change slightly by the time they're actually for sale, but let's be realistic here. They are still the same architecture that hasn't fared too well against Core 2. Their tri-cores aren't even as good as lower end dual-core Core 2s. This isn't going to compete with Core i7, overclocked or not. Considering how long it's going to be until they come out now, I'll be surprised if it even matches 45nm Core 2s, as those have already matured at this point, and will have over a full year lead by that time.
It's probably just high binned chips with a different socket type for a new dual CPU socket desktop board. To my knowledge, that's what the Phenom FX line was intended to be to begin with, before it was delayed.