Only upside with 4K monitors(for now) for most is that the regular dell 30" should drop in price. You will never such a massive resolution for poker unless you have eaglevision or hate your eyes.
2560x1600 do just fine
, no need to go ape**** with 4k x 3kx.
I think GTO setup is a dell 30" with a 21,5" on the side in portrait mode. Or two, each side while we are at it. (lobbyfest on one, play on 30" and read/Surf on the other)