Easy to take the thread off topic so will make this my last...
Perhaps worthy of more discussion sometime with further investigation.
Maybe I am fortunate that their is no back-light type bleed for the borders on my set. They are as black as blacks on my display from what I can tell so not annoying to me really, the simple matter is it is no different to me watching cinema-scope movies. Even with the HD530 standard display software I am running a 1920x810 desktop no problems. Not sure if this is common on many newish models but my TV also has quite an advanced scale/zoom mode.
I can set the 1920x810 which seems to be displaying fine and actually use the TVs own manual stretch feature to make it look taller or indeed full screen 21:9 within the 16:9 ratio if I wanted. Not ideal of course and I guess similar in principle to how some 21:9 monitors will do the opposite using their internal scaling to stretch a 16:9 source horizontally to fill the 21:9 screen.
I understand their are specific apps for advanced screen resolutions and even panel over-clocking that may force games to use a set mode. Yet I wonder why more people with say 50"+ HDTV do not try such and have effectively a 21:9 ratio display format that is much larger than current 21:9 displays offer. Sure you are right about other benefits true 21:9 monitors bring but like I said from my own perspective if I want to gain a 21:9 cockpit view it is a FREE working solution.
A) As for a 1070 and the equivalent pixel count of triple 1080p monitors or a 3840x1620 not being possible? It obviously depends on the game being played, I am from my perspective referring to various racing games and plenty of people play such in triples with cards with less grunt than a 1070. Perhaps yes not with all the highest settings but certainly doable for 60fps and still looking good. Obviously if referring to the most taxing and latest titles this is not the case.
B) Your 2560x1440 = 3686,400 Vs using a 4K HDTV with 2560x1080 = 2764,800
The point being with 2560x1080 the GTX 1070 should perform rather well. If a user has a 4K TV with no back-light issues or is not annoyed with black bars (assuming they watch lots of movies with such anyways) then they could potentially buy a 50" or even larger 4K TV have the benefit of that and also potentially a much larger sized 21:9 ratio display working on it. I make reference here to sofa or racing cockpit type playing scenario not a traditional desk based one.
Will it have g-sync/freesync and offer similar response times as a gaming specific monitor, certainly not.