You have to wait till DisplayPort 1.3 to even dream such a thing reliably. Majority of those who are even remotely of even thinking of gaming 4K w/ something like a 120MHZ will have to wait till DisplayPort 1.3.
Asus themselves stated so, knowing that serious and competitive gamers wil be better off with their line of high-end monitors specifically suited for high-end gaming like the Asus ROG Swift (their flagship) w/ GSync or a BenQ equivalent coming soon.
These monitors aren't for gamers, but they're teased to them occasionally, like the TitanZ.
Gamers are better suited having IPS WQHD displays with GSync, 120Mhz displays. It's a no brainer.
That said, monitor manufacturers have had to start somewhere. It can only get better as DisplayPort 1.3 is available and the inevitable Thunderbolt 3.
NVLink beasts from Nvidia and the things AMD is thinking up for their GPUs also makes it more sane to wait. There's a reason no PC manufactor dared to really create any desktop beasts this Fall until PCIe4, DDR4 Ram, Intel Skylake, and Sata Express are available.
