It saddens me there's been no refresh of the TBD for so long, although I can understand why given the conundrum as discussed above. I hung on and hung and hung on, but gave up waiting, bit the bullet, and bought the current one in October last year once it was pretty clear there wouldn't be one coming along with Mac Pro at launch.
I had to grit my teeth buying such old tech at such an inflated price - I don't upgrade that often, but when I do, I always buy within the first month of a refresh - but I got sick of using an old Dell U2711 with my late 2012 Mac Mini, the delay resuming from sleep, the occasional power cycling I had to do because it wasn't recognising the DP, bah, drove me insane. I also really missed the brightness controls and, yes, built in speakers (for podcasts 99% of the time, for which they are fine).
I did think long and hard about the purchase, and came to the conclusion two things that bugged me most about the current TBD are USB 2.0 and the crazy price for an old display. The 1440p resolution is fine for me, in fact I still adore the display, and as I intend to use my maxed 2012 Mini with it for several years to come, I doubt that'd handle 4k very well anyway. I'm fortunately reasonably well off so the stupid price didn't kill me, and I use the crappy USB 2.0 ports for all the non-speedy stuff like mice/keyboard/lightning cable etc. Around the same time I bought a 15" rMBP, but I've no intention of hooking that up to it anyway.
I did consider the alternatives at the time, came very close to buying a Dell u3014, 30'', far better specced, USB 3.0, 1600p, ports up the kazoo. But I only wanted a display for my mac mini, my old 1440p Dell is used for my PC (where it actually works perfectly) and sits beside it. Plus, amongst all the reviews I pored over re: the U3014 at the time, there was some mention of occasional problems with sleep/resume and the DP, gah, which put me right off.
What is really annoying is that several years ago, for some inexplicable reason, I sold my old 24" LED Cinema Display. Incredibly dated now obviously, but if I hadn't sold it, I'd probably have stuck with it till 2015/16 or so when, presumably, there may be another Apple Display.
Oh yeah, don't shoot me, but I love glossy. I don't do colour sensitive work and can control the lighting. The panel in my u2711 is identical to the TBD iirc, but the Dell has a very aggressive anti glare coating and the TBD looks soooo much nicer for my usage.
Sorry for the ramble.
tldr; bought ATB when it was FAAAAAR from a good deal (actually a complete rip), wouldn't recommend anyone else doing it, especially now, but nonetheless love it and don't regret it in the slightest.