The hardware can theoretically do this, although I’m not convinced a Mali 400-MP can actually decode 4K30. It can definitely handle a 4K framebuffer at 30Hz, but that’s not the same.
The problem isn’t hardware capability, but rather as I said, vendor support. AllWinner are not interested in working with the open source community, so Kodi developers do not particularly care about working on it. CedarX is open source, but I do not know if it exposes enough functionality for Kodi
The Pine64 is cheap because the SoC provider are using IP and not playing fair game with open source:
The Raspberry Pi would be cheaper if the Raspberry Pi Foundation did not have to release any source code and did not maintain firmware or the kernel.
I would recommend a Raspberry Pi if you are shopping in the ~$20 range. If you want H265, then I would wait for the Vero 2.
Pine64 supporting 4K decode is great. But without the software to realise it, it’s just another unfounded claim. I would not purchase the Pine64 on the basis that it may one day support 4K video playback on OSMC.
I will never support AllWinner hardware with OSMC until they change their attitude. Of course, nothing prevents someone from forking OSMC and producing some unofficial builds.
Sam