Android 4.3 is out in the wild, all my Nexus devices updated last night http://www.extremetech.com/computing/162667-google-slips-trim-support-into-android-4-3-to-end-io-lag
My Nexus 7 got the update yesterday. Bit of a problem updating it since it has been rooted and has StickMount on it. Did it eventually though and it seems ok so far...