First high DPI screens are the modern requirement - so 4K if you are offering a high end screen is really just intelligent marketing. People who will pay for the OLED premium are likely to want 4K as well.
Secondly these are made by Samsung, which you can connect because at CES Samsung announced the availability of 13.3, 14 and 15.6 OLED screens for laptops. LG is using all of its capacity for TV's. Samsung's phone sales have been down, panels to Apple are less than forecast so they have the capacity to offer other market options. This is also why they are coming in high DPI because the source manufacturing is there to support it and it then creates a "premium" high DPI product.
Everyone is interested, but I'm sure that price will hold a few back because no one talked the mark up for the screens. Due to cost improvements over the years it won't be as huge as it was years ago, but it won't be free for sure. And today's GPU's can drive 4K at plenty good FPS. For those who desire lower res, just run at 1920x1080 and with the visual fidelity of the base DPI of these screens you will probably be very satisfied. Really this offering will cover all bases pretty well.