Sure, but even then 32bit legacy mode disappears.
Seing how the 64bit amd kernel works so far on SnowLeopard I'm guessing it would take a lot of effort to make it work at all, and even then you can't run 32bit apps.
Well thats what the current situation is on SL at the moment.

Anyhow, I'll gladly install Lion on my MBP, going for 64bit kernel only seems like the right move