Gonna play the devil's advocate for the sake of discussion.
In the near term, I think you're right. I don't think the existence of Stadia is going to result in major publishers releasing native linux games.
However, there are a bunch of factors where I think Stadia definitely will benefit Linux gamers.
- Aggressive moves to streamline the Linux stack (kernel, drivers, api, etc) for gaming. Valve already got this ball rolling and with Google entering the field, it's only going to get better. Much of that will go upstream for all of us.
Stadia is a project that has likely been in development for years, it not something you pull out of the hat in a month, and there's been no indication of Google actually contributing back much in terms of kernel/driver/api, and I don't see this changing. You need all possible technological edges over the competition to win in this market.
There is an exception to that, tho. Google is the main developer of the HLSL (DirectX shading language) to SPIR-V (Vulkan binary shader format) cross-compiler, to ease the process of porting DirectX games to Vulkan. They had a conference on that at GDC 2019 as well.
- Increased support and even preference for Vulkan on Windows games. Rage2 on PC *only* provides a Vulkan renderer on Windows. I think we're going to see more of this, and it means an increasingly smooth Proton experience on Linux. ProtonDB reports a "gold" performance rating for Rage 2. As long as devs don't use awful DRM schemes, Stadia's push to Vulkan should mean an increasing number of brand new AAA games will work out of the box with Proton.
There's no indication of that so far, Rage 2 being the exception. But that's not only on Stadia, but co-developed with id Software, pretty much the only AAA software house using Vulkan instead of DirectX on PC.
Microsoft consoles are and will still be an important target (more than Stadia unless they manage to shake the market from the ground up, which is unlikely with PS Now and xCloud) and DirectX 12 usage is required on Xbox. On top of that you get all the tools (where Vulkan is still lacking (especially on Nvidia's side, although recently there's been some improvements), and free Microsoft support if needed.
- Linux codebase only helps for the future. If something changes to the market ecosystem, if Chromebooks start shipping discrete GPUs. If Valve takes another stab at Steam Machines. If Windows blows up spectacularly and more OEMs offer a Linux pre-install option, then thanks to Stadia, many games will be ready to run natively with minor effort.
These are a lot of huge
if. People said the same with the Steam Machines, and the same when Proton was released.
And even if this was the case and the Linux market blew past the 10% or so to make it profitable, a game for Stadia won't run on Linux and would require a notable effort to fix. Certainly not something I would consider
minor. The graphics API is only a side of it, and even that would not come for free as you now have to support 2 or 3 new drivers (Nvidia, MESA and AMD), with their bugs, quirks and performance characteristics.
EDIT: Just to add more fire to the discussion, Amazon Canada is listing DooM Eternal for PC, coming to Linux as well.
Apparently is the only store doing so and Amazon as incorrectly listed games for Linux multiple times before but there's that.
Maybe after the "first" DooM didn't end up shipping on Linux despite being internally in a working state, we'll see the second chapter?
