I just purchased a 27" last week. Here are my thoughts...
If you look at all the branding on the Apple site, specifically the Thunderbolt sections, you'll see that Apple is using the 27" quite a bit. It's specifically mentioned in a number of sections as working with the new port. If they were planning an imminent refresh, I don't think they would have gone through the trouble.
Second, we all know how slow Apple is with refreshing displays. With their track record, it'll probably be another 18 years before they update.
Third, no matter what happens, the LED cinema display will always work. Placing it at the end of the daisy-chain wouldn't be the worst thing. It's not like the display will go obsolete any time soon.
I've got until next Friday to return it, so I'm going to wait until the event on March 2nd, in the off chance they'll update their store along with the new announcements and include the cinema display. Otherwise, I'd say jump in.