I had this issue and the way I resolved it was to connect my iPad via USB to my computer and force a sync the first time after the update. That solved the problem and now my iPad is recognized in iTunes via Wifi and syncs without issue.
I had this problem as well, and went through the various steps recommended by Apple and on other forums. Eventually I just tried toggling the radio button in iTunes for Wi-Fi sync: turn it off, Apply, turn it back on, Apply, and now it is working. YMMV.
I have noticed a WiFi sync quirk associated with IOS-6. The computer's iTunes will recognize my iPod only if it is NOT connected to a charger. My iPad is original and is still on IOS-5. It functions properly.
Disconnect the iPad from your charger and try again. Exit iTunes and re-open it.
I had the same problem: brand new iPhone 5 could not sync over WiFi. Restore, repeated USB syncs did not fix the problem. But I disabled WiFi Sync in iTunes, applied the change, enabled WiFi Sync in iTunes, applied the change. Now it works.
Yes, for me too. It seems to forget the connection. But going through these steps quickly seems to solve the problem each time. It's a pain, and it didn't use to be an issue, but it's also not catastrophic.