I don't think they'll let the ppc people down yet. I can buy a quad core G5 n the Apple store TODAY, and would be very, very upset if the next big Logic wouldn't run. I'd give it a year or 3 before they go intel only.
I think it will run on any Mac processor, but, like Tiger, it will work, in theory, on other Intel processors because [speculation] it will be capable of running independently of its OS....