I mean...of course they have a roadmap. They had a roadmap well before the first unit. Their work and investment in Proton wasn't just for desktop Linux users.
There are a lot products from steam that got discontinued like the big predecesor, the steam machine. I think a commitment like that is something good.
If you check out The Final Hours of Half-Life: Alyx, you can see a timeline of all the stuff Valve worked on since they started with hardware. Work on Proton started basically immediately after Steam Machines launched, in response to its library problem. So in a way, this is still that same commitment.
True, but they got discontinued because they weren't selling, long after the market itself had given up on the product. It's not exactly like Sega where they came up with a bunch of platforms only to cancel them after a few years.
Steam Machines were more of a collaborative product, not something that Valve really put effort or resources into like Steam Deck. That said, I think a console-PC sold and sponsored primarily by Valve could work.
(After that, I think the initial Steam Machines project - which was imo intelligent - could have some value.)