There are 2400+ Tbred B Athlon MPs and I also saw something somewhere about 2600+ Athlon MPs with a Barton core. AMD will be producing 266 FSB Bartons as they need their Athlon MP line to carry them into the next level.
I think the fastest FSB I've seen available on Athlon MP mother boards was 150, so 166 might not be possible... I could be wrong but I doubt you'll get any high FSB out of an SMP Athlon solution, the goal there is more on stability... extra cache in such a situation should help out AMD MP platforms against Intel's Xeon. Last I knew Athlon MP solutions are slipping farther and farther behind the Xeon, although they utterly crush the price performance aspect. 2600+ Barton MPs could pump some new life into the dying Athlon MP, but like bgeh said, AMD seems to be concentrating on their new CPU line and therefor will not refresh their Athlon MP chipset to support higher FSB speeds.