On Thursday, March 26, 2015 at 6:52:13 AM UTC+13, wrote:
4K is a long way off from being mainstream. If you shoot in HD, your fine. Shooting in 4K is nice, but you'll have to get software to take it down to HD quality for general circulation.
Only film/TV studios are shooting in 4K. It'll be a long time before we have 4K TV's in our homes, as the cable companies only recently upgraded their systems to handle HD.
This is what I know from a friend who shoot's movies in the "industry."

YouTube has supported 4K video since 2010. It's 2015 now. Here's one:

https://www.youtube.com/watch?v=iD4qsWnjsNU

The latest iMacs come with 4K (in fact 5K) monitors. You can readily buy 28" 4K monitors for $400 - $500 e.g.

http://www.amazon.com/DELL-inch-Ultr.../dp/B00I0H9T5C


Maybe there aren't commercial TV shows or movies being distributed in 4K yet, but that's no reason that you can't start now yourself, when a 4K GoPro and 4K monitor are cheap and you can put your 4K movie on YouTube for others to watch.