I'm still not quite understanding some of these conversations.
My GoPro Hero 4 Black model has 4K, too (though I shoot video in 2.7K). For that camera, and my P3P (where I do shoot in 4K) -- the main purpose for me is to be able to crop, pan & scan, and zoom videos using Premiere Pro CC 2015.
The end result (again, for me) is to end up with 1080 or 720 for uploading to Vimeo. I also like 4K video for grabbing high-quality still shots from video segments. More pixels is always better for any type of editing.
Bottom line -- The end result of 1080 is plenty stunning for most computer monitors and human eyeballs.
And even if you're watching on a 4K monitor, unless you put your head right up against the screen, or it's in an IMAX theater, it's still only occupying a small portion of your vision, so there's a point of no return.