I would only get a 4K monitor if it's the same or better than my existing display in every way. That means it should do at least 120hz, glossy, backlight strobing (Lightboost, etc.), and ideally gsync. It could be a long time before such a monitor comes out, especially since DP 1.2 doesn't even support enough bandwidth for 4K at 120hz, although if it does I would be willing to pay big bucks for it. The performance at 4K is less of a concern for me, as I would just run modern games unscaled at 1920x1080 and stick to older ones for 4K. 4K is probably the first resolution that can run at 1/4 size without scaling and still look decent.