[BurningCycles]

My guess would be AV1, on the other hand this is really the space h265 occupies at the moment so maybe they will be effective at holding on to it.

I fully expect AV1 to become the new 'de facto' video format on the web which is the crown h264 has held for ages. No royalties, better compression and wide hardware support coming will make it a very attractive choice.

And as streaming will also move towards 4k+, given that all the streaming giants (Google, Netflix, Amazon) are directly backing the development of AV1 it would surprise me if they did not phase out HEVC in favour of AV1 for all their 4K+ needs as well (Youtube doesn't support HEVC at all).