Personally I think there’s a case for a more powerful and more flexible device. AV1 playback is certainly essential on a next gen device, but I’d like to see something that can handle literally any video you throw at it, including Hi10P playback up to 4K, and h.264 up to 4K60 rather than 4K30.
On the sort of timescale we may be talking about, 8K playback may be becoming a necessary checkbox feature, too.
Something powerful enough to decode 1080i/50 and 1080i/60 in software would be good, so we can take advantage of software-mode deinterlacing. (Although sadly, so long as VC-1 software decoding remains single core, I doubt that will ever be doable for VC-1).
Enough power to upscale to 4K using Kodi’s higher-quality scaling algorithms (like lanczos3) might be interesting.
Something that can transcode 4K HEVC in real time might be good, so it can act as a stand-alone Plex server.
USB 3.0 ports are definitely needed, preferably supplying enough juice that you don’t need a powered USB hub, and bonus points if there are four genuinely independent USB ports rather than two.
I’d also like something that supports Widevine L1 and is recognisable as a certified device for Netflix, Disney+, etc. I’m so tired of other Internet steaming-media players with crappy image quality and/or no resolution or refresh-rate switching!
And although Sam almost certainly doesn’t agree, I think both single- and dual-layer Dolby Vision support will be essential.
Clearly we’re talking about a far more expensive device here; but there are £300+ media players out there; there’s a market for them.
EDIT: And,come to think of it, something powerful enough to render BD-J blu ray menus without the need for hardware acceleration would be great too.