I currently game on a 27", 1440p 144hz g-sync. Briefly went to a 35" ultrawide but didn't care for it so back to my 27". I sit about two feet away from my monitor, I cant imagine anything bigger than even a 32" on a desk without it just being too big. I assume your sitting across the room? Or not at a desk?
And as other have pointed out, their Big Format Gaming TVs will be out soon, 4k 140hz 65" g-sync, etc etc. Cant imagine how much those are gonna be.
I sit about 3 feet from my 40". I wouldn't' want anything bigger that's for sure. Great perceived viewing area coverage from this distance.
I looked at the 42" 4K Korean displays(Wasabi Mango, etc) before choosing the Samsung because 40" was the perfect size and I got it from Best Buy so exchange/return was just a 30 minute drive if there was any issues with it.