Is the Thunderbolt display released in 2011 retina display? I know its not 5K, but is it retina? And when can we expect a 5K one to be released?
Well, according to this site -
http://isthisretina.com - the 2560x1440 TBD is "retina" if you view it from at least 32" away in the sense that the average eye won't be able to pick out individual pixels.
That's reaching a bit - in reality "retina" on Apple devices has usually meant 4x as many pixels as the previous "non-retina" device, and support for the new "HiDPI" modes and high-quality, resampled, "scaled modes" that take advantage of that. The TBD can't do that (you can probably use a hack to enable HiDPI but you'll get huge text & icons).
That said, 2560x1440 TBD still looks like a million dollars compared with a cheaper "full HD" 1920x1080 27" displays - but it won't match the pin-sharpness of the "retina" 5k iMac @ 5120x2880.
Personally, unless I succumb to a 5k iMac, I'd stick to 2560x1440 until affordable 5k displays and the computers that can drive them appear.
(Anybody used a 27" 4k screen in "scaled" 2560x1440 mode to give the same text/icon sizes as the TBD? What is it like?)
I don't think there's any guarantee that Apple will ever release a new Thunderbolt Display. The fact that they didn't update the existing TBD a couple of years back with the new iMac-style screen & body, USB3 and Thunderbolt 2 suggests that it's not a big seller. If they do, it will likely be either Thunderbolt 3 or Displayport-over-USB-C and won't work with current Macs (at least not at 5k - they could produce a 21" 4k display).