I'd like to see:
-3D Maps app
-Siri
-Make the new tab navigation feature in Safari show ALL the tabs when you pinch in an expose view, rather than the swiping UI we have now.
-iCloud Documents overhaul. Get rid of the silly iOS interface. Allow for fully nested folders, and let me see all the documents that the app can open, rather than just what the app created.
-Signs of a new filesystem in the works.
-Pull-to-refresh in Safari and Mail.
-Weather widget in notifications
-Dictation that works as you speak
-cloning functionality in disk utility
Things I don't think apple would ever do, but would be great:
-Tabs in finder
-Color back in sidebars
-Set Library visible as default again
-iCal, Notes, Contacts looses the skeuomorphism
-Lose the sandboxing, or at least make many more entitlements so apps that had to leave the MAS can come back.
-Remove automatic termination
-all window expose as a separate view/key from mission control
Every OS X release from here forward should be low on the feature count, since they're moving to yearly releases.
There is already cloning in Disk Utility, just click the drive you want to clone, click the restore tab, drag Macintosh HD (or your main partition) into the "source" field. Then drag the volume or partition that you want your main partition to be copied to into the "destination" area. Then click restore (this will erase all contents off of the volume or partition).