Yes, You Can Upgrade a Mac with Snow Leopard Directly to OS X Mountain Lion
Mac OS X Snow Leopard can be upgraded directly to OS X Mountain Lion, assuming the final release maintains the same capacity as the currently available developer previews. To perform the direct upgrade as it stands today, users will need to have created an OS X Mountain Lion USB installer from which to boot off of and upgrade with, though there is a possibility that a Snow Leopard Mac will also have access to Mountain Lion directly from the Mac App Store.
We have received many questions about this in our inboxes and comments and figure with the OS X Mountain Lion release date set for summer it’s a good time to answer it based on currently available information. It’s important to note this upgrade path is based off of the current developer previews of Mountain Lion and upgrade eligibility could change before the public release, it’s also possible that Apple won’t officially support upgrading from Mac OS X 10.6 to 10.8 and this could remain an unofficial and unsupported feature.
A fair amount of OS X Snow Leopard users have held off on upgrading to OS X Lion, but with the release of Mountain Lion around the corner it’s quite likely a lot of OS X 10.6.8 holdouts will jump directly to OS X 10.8 if it is possible. Mountain Lion does have stricter system requirements than it’s predecessor, however, and some owners of older Mac hardware could wind up with Lion being the last supported version of OS X on their machines.
We will update with additional information on the various Mac upgrade paths to OS X Mountain Lion as further details become available.