According to reports, the next version of the Mac OS X could be coming as soon as Macworld 2009.

The weird thing about this rumored version is the code name, Snow Leopard which closed to Leopard (Mac OS X 10.5). Come to think of it, rumor has it that 10.6 will only be performance upgrades, UI changes and switching to being Intel-only, that label kinda starts to make sense. As of the moment, the status of the rumor is unlikely to be true.