more important thing for me is not resolutions but HDR and EXPANDED color !!!! to get 10bits per channel instead of 8bits is a BIG THING
http://www.cnet.com/news/ultra-hd-4k-blu-ray-what-we-know/
"High Dynamic Range: 4KBD will have HDR in the form of metadata, with Dolby Vision and other HDR formats as options. HDR is really cool. Part of this is an expansion of the bit-depth possible with 4KBD."
"10-bit: Both HDR and expanded color are possible, thanks to a higher bit-depth of 10, greater than current HD's 8-bit. At the very least, this means more steps of gradation (no banding, not that Blu-ray had much)."
but I agree with this :
"Sadly, most people won't care. Worse, most people won't know there's a difference. 4K is 4K to most people (and if you're reading this, I'm not counting you in the "most" group). That's a battle not likely to be won by an archaic physical media, no matter how shiny it's marketed as being. Think that's pessimistic? How many of your friends still watch DVDs?"