Acording to this topic, it seems that OS4 for Classsic systems will be avaliable on 30th November.
I wouldn't keep your hopes up, but OS4 does seem to be a lot more 'finished' than it was a few years ago, so it could be that we will be getting a new OS to play with soon.
If it does get released, I will definately be buying a copy. I will just need a PPC to run it on then.
(If you are wondering why I would buy a copy without a PPC, it is to make sure that I will have it for when I do get a PPC - I wouldn't want to risk it selling out, or them not being able to sell it for other reasons.)