There has been much discussion about the fact that Snow Leopard is an "Intel-only" OS. I view this from a few angles.
Firstly, all of this is speculation based on the fact that the Snow Leopard preview DVD was Intel only. This is not confirmation. The build may have been an incomplete preview. PPC support may be forthcoming. Either way, this is hardly "proof" that Apple has dropped PPC support.
That said, I think that we have seen the last PPC supported OS from Apple with Leopard. The improvements set to be delivered in 10.6 are not a boon for PPC systems. There is no confirmation that PPC multi-core systems will be supported by the new "Grand Central" thread model, so that may not be an advantage. And Quicktime X and Mail 4, which delivers native Exchange 2007 support, can easily be delivered via software updates or even an "add-on" DVD that can be sold in Apple Stores. No one has suggested that Apple will no longer make universal applications, which means anything not based on Quicktime X should run out of the box on PPC -- albeit perhaps slower if it's properly multi-threaded.
While Snow Leopard will start to push 64-bit system-wide, there is debate as to whether this is a good idea at all on the PPC platform. So Snow Leopard may not be an attractive update after all for PPC Mac owners. It's entirely plausible that Apple continues to deliver updates to PPC owners long after Snow Leopard hits shelves.
Of course, I do not believe that these technologies will take shape in 10.6 and restore 10.7 to universal status. Rather, I suspect that we'll see Leopard updated alongside Snow Leopard for some time, as much of the core code will be exactly the same. I think this is largely why the codenames are so similiar, because Apple wants to ease the transition. I firmly believe Leopard will be supported through the release of 10.7 Cougar (or whatever), at which time we'll finally see the introduction of a non-PPC compatible OS X which may include massive updates like ZFS as the default file system. By that time, likely in the second half 2010 at the earliest, the newest PPC system will be over 5 years old, certainly a fair timeframe for Apple to move to security- and maintenance-only updates.
What do you think?