It has been a few months now that I have experimented with my UHD set up and I have been able to draw a few conclusions.
My Tv is a Sony KD-55X8505B and as 4K player I use the Tv itself for Netflix (one of the few places you can find 4K content) I have not tried amazon 4K. In order to play your own files you can either connect your TV to a NAS or use a small box.
I went for the Minix X8H-Plus as a media player to stream from my NAS as the client in the Sony TV is pretty basic.
The minix has hardware accelerated HEVC decoding so it will work as a player for any 4K TV that has no compatible codec. A word of warning though the Netflix and Youtube client in the android box are not 4K compatible.
I have an FTTC connection with 32 mbps speed that is more than the recommended 25 mbps for Netflix UHD so I gave it a go and the results are spectacular, not just the Tv shows (house of cards, better call saul, Marco Polo) but the short features on deserts and flowers are amazing. All of this content is HEVC so 25 mbps or less for 4K UHD.
I then tried tears of steel https://mango.blender.org/
Tears of Steel is a short series shot in 4K using the old school H264 codec as the Panasonic GH4 and LX100 do at 100 mbps, the files encoded at 72 mbps end up with a massive 6.12 GB for just 12 minutes.
H265 vs H264
On average at similar parameters the same source compressed with H265 results in 65% space saving compared to H264.
Now that is quite a lot so if you think about it your 100 mbps GH4 file could shrink to 35 mbps which is just a little more than AVCHD progressive and less than Sony XAVC 50 Mbps you can still record it with a class 6 card though class 10 would be appropriate.
Cameras and Editors
Today only Samsung NX series can encode HEVC and for editing there are no programs on Mac using HEVC, possibly something exists for windows. But it is fair to say we are a long way away from main stream.
Why is HEVC important? With H264 the files are too bit and if compressed to youtube average of 25-30 mbps they do not look that good you wonder if it is actually worth it.
A large 70 mbps file require a very fast wireless ac router close to the player or simply using a memory card to play your videos locally. This is not user friendly.
I believe it will take at least another year to see HEVC included in cameras and editors if not longer, until then for me it makes no sense to invest in a 4K set up as the file produced are just too large to be shared so remain in the realm of semiprofessional to professional users.