Palm Cobalt and Mac Support provided a brief preview of the upcoming Palm OS Cobalt featured at the PalmSource conference on February 10th. It appears Mac syncing, however, is not in the works:

Mr. Slotnick .... made it clear that PalmSource isn't developing a Mac version of the Palm Desktop. As the way the PIM apps work has changed significantly, this means Mac users won't be able to HotSync without third-party software.

While a 3rd party (Mark/Space, Missing Sync) is planning on providing this functionality for Mac users, a lack of built-in functionality is unfortunate.