I've been waiting for new Thunderbolt displays to be released. I purchased a new Macbook Air in July and would really like some new displays for my desktop.
If it comes out, I imagine it would be announced with the new iMac. There are rumors that Apple is going to a new process with the iMac display (direct bonding like the rMBP displays) so I would expect the ATD would follow this process, as well.
So you might as well wait until then, though Apple is also rumored to be having yield issues with the 27" iMac display so if the ATD is using the same process, it might be having the same issues, as well.