Speculation about an imminent update to Apple's Leopard operating system has quickened, with at least one site claiming the release of Mac OS X 10.5.2, the second update to Leopard since its October release, may happen within the next week.

The update is expected to be substantially larger than the 10.5.1 upgrade Apple unveiled in mid-November.

Among the anticipated fixes and enhancements expected in Mac OS X 10.5.2, most bets have been placed on changes to the new Stacks feature in the Dock; an option to turn the now-translucent menu bar opaque again; DVD and CD sharing, one of the features CEO Steve Jobs demonstrated when he touted the new MacBook Air last week; and modifications to Time Machine, Leopard's backup and restore application.

Interest is particularly high in this last item, since some reports have claimed that Apple will soon update both Time Machine and the AirPort Extreme wireless base station so that the former can back up to a hard drive connected to the latter's USB port. Some users who bought AirPort Extreme expecting to use its once-marketed – but subsequently disabled – ability to work with Time Machine have been complaining on Apple's support forums since Jobs introduced Time Capsule, a new backup appliance, at last week's Macworld Expo.

The BabyGotMac website, for instance, which has posted the most information about 10.5.2 and Time Machine, initially said that the next Leopard update would allow Time Machine backups to AirPort Extreme-attached drives. Yesterday, however, it posted follow-up information that said although drives connected to an Extreme could be written to and read from under 10.5.2, the update didn't fix the Time Machine problem.

"Sadly, this leaves us in the same boat we were a few days ago," said BabyGotMac. "Hopefully it's just a switch that needs to be flipped when the update is released, or perhaps we'll see the ability to use Time Machine with network/Airport disks available as a paid upgrade (a la [iPod] touch apps)."