We thought it may take a while to start getting Official builds of 4.2 from the Cyanogen Mod team, but it looks like we are in for a treat. They posted the first nightly build of CM 10.1 for the Verizon Galaxy Nexus today. They have also posted from Google+ that you should be able to go from cm10 to 10.1 without wiping data. They have also tested this on several older devices. So far it looks like the clock app is not working properly since cyanogen's stopwatch and timer functions don't mesh well with Google's own implementation of those functions , but you should be able to fix it by clearing app data.