The HDMI Forum, responsible for the HDMI specification, continues to stonewall open source. Valve’s Steam Machine theoretically supports HDMI 2.1, but the mini-PC is software-limited to HDMI 2.0. As a result, more than 60 frames per second at 4K resolution are only possible with limitations.
As long as the manufacturers are competing against each other, that’s never going to happen.
The “gamer” consumer demographic has some of the most whiny, entitled vocal minorities. They’re going to endlessly complain about the next generation of console needing a special cable/dongle to connect to their TV, one of the manufacturers are going to fold, and then the other one is going to walk back the lack of HDMI because they don’t want to lose sales to their competitor.