Ok, somebody has to ask crazy questions around here, and I guess that has to be me.
It looks like Haswell will decode 8K H264 bitstreams, but with the MFX_WRN_PARTIAL_ACCELERATION, warnings, and quite possibly all in software. Meaning there is a Huge performance drop relative to decoding 4K. [in terms of output pixels/persec or output GB/sec, not FPS]
[I get about 250fps decoding 4K H.264 with Haswell, but about 12fps decoding 8K H.264 with Haswell]
Can Skylake decode H.264 8K (7680x4320) without MFX_WRN_PARTIAL_ACCELERATION?
8K HEVC encoding is not available on SKL due to hardware design. Also, any of the above information is applicable to Media SDK Client and not to Media Server Studio. Media Server Studio plans on SKL will be officially released in sometime. Stay tuned!