It seems a bit unlikely to me but a rumour popped up that AMD might have some really nice Phenom FX parts in its upcoming 45nm lineup that might give Intel a headache. A website called Reviewage claims AMD has a 4GHz Phenom FX-80 and a 4.4GHz Phenom FX-82 on its roadmap. According to Reviewage, the 4GHz Phenom FX would be faster than a 5GHz Intel Kentsfield. I'd take it with a grain of salt though, this seems way too good to be true.
Come AMD Deneb core and lot seems to be on offer. To begin with, unlike the Windsor core that had a maximum FSB multiplier of 16.0x, initial reports suggest the Deneb to sport a maximum 25.0x multiplier, 200 MHz x 25 = 5.00 GHz, with the FSB left to play with. Considering at 2.30 GHz the Deneb draws in 57.3 W (according to findings), it should still leave enough room for AMD to sell premium products clocked at high frequencies.
From Reviewage's findings, there seem to be two Phenom FX processors in the making. The numbering seems to take off where it last left at the Athlon64 FX 74. The two chips, Phenom FX 80 and Phenom FX 82 could be clocked at 4.00 GHz and 4.40 GHz respectively (stock speeds). An interesting statement is that at 4.00 GHz, the Phenom FX 80 should outperform an Intel Kentsfield core clocked at 5.00 GHz, implies it has to be faster than the Kentsfield on a clock-to-clock basis.