Intel have announced that plans to offer a 4GHz Pentium 4 processor have been scrapped. Future development for Intel desktop processors will move toward the PentiumM processor technology, which runs at much lower clockspeeds and uses less power consumption.
This move leaves Intel in a position where they will not be competitive with AMD in the desktop market for quite some time to come.
These two articles from the Inquirer provide a quite comprehensive outline of the situation: