I'm trying to fix an issue that is the result of a bug I disovered, and I'm out of ideas to troubleshoot. I'm hoping you guys will have some more suggestions, perhaps deleting plists or somehow resetting iTunes device syncing so I can start over.
Using Setup Assistant to transfer data over from my other parition which had iTunes configured to sync my devices causes the new partition's iTunes to NOT show devices in iTunes. When I plug my device in, the option to sync over Wifi is still enabled, but unplugging it still doesn't keep the device displayed in iTunes. Unchecking Wifi sync, clicking Apply, checking, clicking Apply and disconnecting results in the same problem - device disappears from iTunes. But if you go to Settings > General > iTunes Wi-Fi Sync, the Sync Now button is not grayed out. Clicking it starts the sync, but it never gets past the "Looking for iMac" stage.
I'm in the process of filing this bug with Apple, but I want to include the steps I've followed to fix the issue so they know.
What I've attempted so far (in this order):
Quitting and relaunching iTunes
Restarted my iPad
Then forcing a sync on the iPad via Settings is the same result, endlessly looking for the iMac
So then I opened AirPort Utility, clicked my Time Capsule, then clicked Base Station > Restart. After the Time Capsule restarted and the Wifi was working again, I checked back in iTunes to see if the iPad showed up - it didn't.
So then I turned off Wifi on the iPad, Quit and relaunched iTunes, then enabled Wifi on the iPad and it still didn't appear.
Note that the exact same thing is happening with my iPhone.
OS X 10.8.3
Not even deleting plists, essentially resetting iTunes, solved the problem.
In case anyone has troubles with this and none of the troubleshooting steps worked, here is your last resort, which finally solved the problem for me.
Use Terminal to delete iTunes:
sudo rm -rf iTunes.app/
Download and install iTunes
The iOS devices magically appear in iTunes, without needing to plug in via USB to enable Wifi sync.