From https://repo.steampowered.com/steamos/README.txt
SteamOS version 1 'alchemist' and version 2 'brewmaster' have been discontinued. No further updates are planned.
The SteamOS 'clockwerk' prototype has also been discontinued and will not be released.
Some of the recent SteamOS release notes have included references to Asus's handheld, which has reinforced the community expectation that it will eventually be available as a distribution you can install on 3rd party hardware. If you go read interviews from Valve employees (Lawrence Yang comes to mind), I believe they've publicly stated that after the OLED shipped, they wanted to start focusing on porting to other devices.
If so, it is kind of bizarre they haven't reached out to the Bazzite maintainers at all.
In general, it seems like it would save them a tonne of effort if they'd switch from a bespoke Arch-immutable spin to making a spin of Silverblue, something that has been meant to be immutable from the beginning.
They already have a system that works exactly how they want it. They already rebased from Debian to Arch to get it there. They have enough Linux staff on contract to build and maintain that system.
Maybe Bazzite is closer to their goals; maybe it's not. It's certainly not a slam dunk that the best thing they could do is throw away the thing they've been building for years to join a community project on GitHub that's trying to clone that thing.
But I haven't heard anything one way or the other in a while. But as it stands, they have stated that they plan to do a general release. Unless there is another source where they say they changed their mind?