"Whatever the reason, the result is a much wider 4K app lineup with the Roku 4, which always outputs in 2160p (with an upscaled 1080p interface in apps and menus). In addition to Netflix and Amazon, users can buy or rent 4K videos from Vudu, M-Go, and UltraFlix."

http://www.techhive.com/article/3034683/strea...aming.html