I didn't think anything was being broadcast in 4k yet. There is a 4k Blue Ray coming, but even it's not available yet. I think Netflix and Amazon are streaming some 4k now.
Instead of buying a stand alone 4K player buy a new Xbox one S. Then you have a 4K player, 4K streamer, roku type box all in one. And it plays games if you want to do that.
I think the content argument is strong. No point in owning a 4k tv in my house that I sit 15' from the screen when all its going to display is 1080 content upscaled.
Nice TV's for sure, but with three kids I don't need to be in this pool until it has some water in it. This from a guy who was an early adopter for years.