There are no fabs currently capable of producing either display type in quantity, however they are being built for both. OLED said almost 10 years ago that it would be coming soon and it still isn't here, but it is closer to actual production than 4K. The problem is, and again that is the reason why they are expensive, is the yield is low. The process to create them is still in infancy, so it will take time to bring the equipment and processes up to speed to make them cost effective, and that also applies to 4K. Technology wise, 4K can be built now too, but I think it is not going to be in mass production as soon as we'd all like. There's no doubt we will see both on the market (including 4K OLED?), but they likely will end up competing in different niches; likely only one or the other will stick around though. All of the display manufacturers are being cautious at this point, focusing more on the new technologies and manufacturing cost reduction to increase profit margins as opposed to pushing out a lot of cheap TVs.
