Leopard will be availble for both PPC and x86 Macs, no doubt about that. How they do that will be very interesting though. I bet they won't sell it as retail for their Intel Macs, only their PPC, because all their Intel Macs by then probably will ship with it.
I think Leopard will be a much more minor version of OS X. I can't really imagine what will be its biggest features - definitely compiled as universal binary, or however they'll do that. But beyond that it's all blank. Anyone have any ideas? If they won't be featuring it until WWDC 2006 and they want it out by the end of 2006, that leaves developers little time to test their apps, so hopefully just small general changes and no major API changes either.
2006 - the year of Intel