The TB display is only a year old. The design is two years old, as it is identical to the design of the 27" non-Thunderbolt LED display. I hear ya though, the improvements made to the 27" iMac solely in terms of the display have to come to the Thunderbolt display at this point. Obviously, MagSafe with a supplied MagSafe 2 adapter will simply be replaced by MagSafe 2 (leaving owners of original MagSafe and Thunderbolt equipped users out in the cold in terms of charging their stuff [oh well, standard Apple for ya]) plug, USB 2.0 ports will be replaced by USB 3.0, and the FireWire port will be dropped in favor of a second Thunderbolt port; the Gigabit Ethernet port will remain. It's inevitable and, at this point, it's almost a no-brainer. My only hope is that they continue to offer the "current" non-Thunderbolt 27" display as there are tons of people stuck with machines without Thunderbolt but still in need of such a display (such as every Mac Pro owner).
Yea, I think they'll have to keep the LED Cinema Display around for awhile given all of the non-TB and non-MagSafe 2 Macs out in the wild. What they really should do is discount the price of that model given that it was released in 2010, has no TB ports, USB 2, VGA web cam, etc. $799 sounds about right, but wouldn't count on it.
I'm really excited to see what they do with the new Thunderbolt Display though. In theory, they should be able to get it as thin as the iMac (if not thinner) without any bulge in the back. Of course, they'll still need enough depth for the ports, but it should still look really nice. I know the thinness doesn't matter much for a display, but it would look really sexy on my desk connected to a 13" rMBP. I could see myself keeping that set up for 4 years or so but who knows. ;-)