Interesting thread. Following a tea and laptop accident in 2021 I bought a macbook with XDR display (P3 gamut and 1600 nit max) so have tracked the HDR evolution with interest.
It seems to me that the various approaches reflect the nature of the businesses involved.
Dolby has historically provided a new high end standards e.g. PQ 10,000 nits max.
Adobe with a huge base of legacy users/images has pursued a bridging approach jpg + GainMap.
I expect Google has their own business interests in minimizing image transport/retention and the number of formats to efficiently support.
The hardware vendors will push out new display hardware as they can differentiate it, produce it, and sell it. Apple with XDR. VESA (PC trade group) has a multiple tiers of max luminance (400 500 600 1000 1400) https://displayhdr.org
My cursory look at OLED is that while there is wide adoption for the larger area lower pixel-per-inch televisions, and smaller area higher pixel-per-inch phones/tablets it will still be a few years before they will be commonplace for computer displays medium area medium pixel-per-inch.
I expect there will need to be some bridging solution given the large based of displays and images, and maybe a separate final next generation standard based on technology that may not yet exist. So, it seems to me a big part of a solution is how the navigate the next decade while all this is sorted out. Specifically, how to produce images that can be rendered optimally for a target but sufficiently well elsewhere.