Re: So the comparison could be...
Turion with 64b vista and 64b aps (when they are available)
versus a Yonah with 32b vista and 32b aps.
If you are speaking of Vista at all, then the correct comparison is with Merom, not Yonah. I don't expect Microsoft to pull in their next generation OS any sooner than the Merom launch.
I do agree that some Yonah consumers will want decent performance for upgradability to Vista later, but the vast majority of buyers are going to compare performance using current operating systems, since future performance is only speculation, at best.