If I remember right, I saw on JCs that the P4 will debut at 1.4 - 1.5GHz, with 1.7GHz+ in Q1/2001, and 2GHz+ in Q2/2001.
If AMD can keep up, the P4 will most likely be dead in the water.
I'd be willing to bet that AMD could release a 1.4GHz Thunderbird on current process technology, maybe with a little tweaking. At least 1.3GHz. When Mustang comes out, with it's slightly longer pipeline, and hopefully other tweaks, I bet it could do 1.5-1.7GHz. Sledgehammer will supposedly do 2GHz+. So unless the P4 can ramp to like 3GHz+, I don't think AMD is out of the MHz race, at all.