Besides other things video related (including big ones like mobile battery life and video playback without the fan going into vacuum cleaner mode when viewing 4K HEVC video, as well as multitasking during such video playback), don't forget about one very huge feature which is 4K DRM support: Netflix 4K, Sony 4K, etc. don't work at all on Skylake.
Eventually there will be GPU support but right now even the latest high dollar GPUs don't support it. So if you already have Skylake desktop you can hope that your $$$ GPU eventually gets support, or else you can hope to spend even more $$$ when a new GPU model gets support. If you already have a Skylake laptop you'll probably just have to accept it will never get proper 4K streaming support. If you are buying a CPU for 2017, the only option IMO is Kaby Lake (or later), if you have any interest in streaming 4K.
One can argue about whether or not 4K DRM is evil, but the bottom line is that 4K DRM has effectively obsoleted anything older than Kaby Lake, for people interested in legal 4K streaming.