good question, also does anyone broadcast it. don't think so.
...oh thinking a little Netflix and amazon are starting to have some 4k content, I suppose others will follow.
but 4k blurays would require new players and probably break the standard, or rather they will extend it.
will be interesting to see how they will get around that, so you actually can own the movie on a physical media.
there is a few Netflix rips out.
the addon does not care about the resolution, as long as your box/hardware and player support it.