Assuming M2 and AM2 will actually be different sockets that means when/if K8L will be out before the end of 4Q07, 940pin AM2's lifespan would be just a bit more than a year. It wouldn't make sense for AMD to release a socket that's supposed to be around only for a time that short.
But if M2 and AM2 procs are compatible, there's really no reason at all to "skip AM2". Although, there are other things that point M2 won't be compatible with AM2:
Quote Originally Posted by s7e9h3n
Socket M2 is going to be initially released as 940-pin, DDR2. In ~6months time, M2 will make the switch to 1207-pins.
LGA1207 is needed only for making quadcores possible.

In a PDF from Phil Hester's (AMD Chief technology officer) presentation at AMD Analyst day there's only one mention about quadcores: they will be out with the "new core" (K8L). So, there will be no quadcore rev-F procs. This means if "AM2 will go LGA" "in ~6months time" K8L would actually be out very early 1Q07!