Socket M2 will be revising the K8 architecture with Revision F...which basically means modifying the memory controller for DDR2 support, however, from my understanding, RevF memory controllers will be capable of supporting both DDR1 and DDR2 therefore it is likely there will be backwards compatibility...of course your processor would most likely be bottlenecked as AMD is using DDR2-667 standard and the current DDR1 standard is DDR400
That said, socket M2 is being hugely overhyped. It's still using K8 architecture with the only difference being support for DDR2...however with AMD64 LDT bus your benefits over DDR1 will be minimal and I suspect the reason AMD has migrated to DDR2 has been pressure from memory manufacturers to do so...furthermore DDR2 still has poor ICs and terrible latency issues making it a poor memory platform altogether
The only relatively interesting thing to RevF processors is Socket S1 which refers to a low pincount socket designed for mobile processors. Based on the AMD roadmap and based on what current Turion specifications are one can speculate S1 will be the breeding ground for the next XP-M style family which of course means unrivaled overclockability...however with so much success with numerous cores (eg Winchester, Venice, Venus) I don't know if there will ever be another mobile family of processors like the XP-Ms and their infamous overclocking
What am I getting at? Socket M2 is nothing different from Socket T...different pincount and a different memory platform, but performance wise, not much of a difference. Don't get tricked into what many people already believe. You would be better getting a socket 939 processor now as they're very capable and very affordable and then waiting for K9 and DDR3 or XDR