I know that the 4k can handle 1440p 60hz, but that some people have had issues with blur and ghosting. If you could run 1440 in an interlaced signal, at 120 fields per second, it might reduce blur. Just a thought.
Old CRT TVs used to be limited to 30 progressive hz interlacing allowed for 60 fields per second, reducing flicker.
I think a 60hz display refreshed at 120 fields per second would be very smooth.
Doc-Ok and Carmack seemed to think that this could reduce latency. Its worth an internal test if the team has time.