Given the fact that 4k monitors are going down in cost at a moderately rapid pace, and that this game is expected to be around for about ~6 years, it would seem that 4k support should be a priority.
By then, 4k will likely occupy the mainstream and 2560x1400 will be perhaps more lower end in desktop monitors.Perhaps by then 6k and 8k monitors with 4:4:4 subsampling will become high end.
I know that there are plans (in SK as well) to make the UI size adaptable, but is there anything else?
On that note, will there be any support for multimonitor?