The next P4: Prescott
Intel unveiled the code name for the next iteration of the Pentium 4 today: Prescott. The best report on the subject that I've found is here, but they're all pretty short on details. We know that Prescott will debut next year. It will finally incorporate HyperThreading tech in a desktop chip. And Prescott chips will be manufactured using Intel's 90-nanometer manufacturing process. Intel is hinting that the chips will run as fast as 4GHzat least.
Beyond that, I'm thinking the chip won't include many changes to the basic Pentium 4 design, because Intel spent a lot of time pushing form factors, USB ports, and I/O standards in its talk about Prescott. But I could be wrong.