http://techcrunch.com/2014/02/07/shutterstock-adds-4k-video/
Not sure that it's directly relevant to those of us who don't submit video, but it does indicate that SS isn't just resting on its laurels, which is a good thing
Interesting. A current day Epic M Red Dragon is a mere $50,000 for the body only. But Panasonic makes a new DSLR G4 with 4k video for under $2,000. Looks like most DSLR's will be outfitted with 4k in the near future. I am sure cards, software support and memory will be an issue.