In theory everything is possible. I imagine we get Ray tracing eventually now that amd says they have it coming with their next round of GPUs. But it's a lot about cost so imagine at best it's 2 years away. Stadia has to scale and for its price point we are never going to match high end gaming PCs graphically.
The promise from Stadia was to have the best quality. They showed some muscles some months ago and talked about terraflops etc like other competitors can’t match...
so they better have high end systems
Raytracking is still quite new but Physx is a necessity for games like Borderlands. Currently stadia can't even reach the technical level of a 2010 gaming PC.
Here is a Physx demo video: https://youtu.be/n5qhaEghJ74
And here a Raytracing demo video: https://youtu.be/SsngvOXLMIY
Dude let's all be honest here bc ray tracing is a joke.
PhysX is an nVidia feature, Stadia is based on an AMD GPU so it definitely won't be supported. PhysX can be done in the CPU, but I don't believe anybody will be using any nVidia libraries for Stadia games.
As for ray tracing, it's the same deal. It'll probably have some implementation of it, but it won't be RTX.
Will agree with @BinaryJay regarding PhsyX, that's an Nvidia feature that is probably proprietary so little to no chance seeing it on Stadia. However, I am certain AMD have their alternative which is opensource. whether developers actually use it is a different thing. Typically on PC, at least, games using Nvidia specific features have had some type of development partnership with Nvidia.
As for ray tracing, I would say, that is more likely. I know on PC, the tech press and hardware reviewers have tended to confuse the lighting effects, the APIs, NVidia Turing architecture design, Nvidia's RTX API software stack they've written into their drivers, DX12 and Vulkan, and what "hardware ray tracing" actually is. I have only come across two people who have really covered what ray tracing actually is.
AdoredTV (https://www.youtube.com/watch?v=SrF4k6wJ-do)
and
Naoki Watanabe (https://www.youtube.com/watch?v=3BOUAkJxJac&t=348s and https://www.youtube.com/watch?v=VdS-baX7hwE&t=133s)
Basically ray tracing is essentially an umbrella term used to cover a series of algorithms for simulating photons in a scene or in physics waves in bouncing off surfaces (https://en.wikipedia.org/wiki/Ray_tracing_(graphics) and https://en.wikipedia.org/wiki/Ray_tracing_(physics) ).
There are multiple approaches to doing this and each one is algorithmic in nature. That is to say, there are step-by-step calculations that various researchers have developed over the years to run on ray tracing devices to determine the path of the rays. So ultimately there is nothing remotely special or unique about ray tracing that would mean AMD or even Google, could not find a set of algorithms that will do the same thing in a way that works optimally for the hardware Stadia is running on. The CryTek's CryEngine introduced ray tracing without needing DX12/DXR or RTX API or Vulkan or Nvidia's Turing (RTX) GPUs (https://www.youtube.com/watch?v=z0kICYkaKo0) and World of Tanks does ray tracing that will even work on Intel iGPUs. This video show the difference with enCore ray tracing on and off better than the demos others have done (https://www.youtube.com/watch?v=Suur7CNYQBk) Pause at 3 seconds in to see the difference on the tanks' tracks. And let's face it, a Commodore Amiga 500 was doing ray tracing back in the 1990s (seehttps://www.youtube.com/watch?v=CBkUzab5TEo andhttps://www.youtube.com/watch?v=5KcwMZUnIAg andhttps://blog.codinghorror.com/real-time-raytracing/)
So since Stadia uses Debian Linux as its base OS and Vulkan as its graphics rendering API and ray tracing is just a suite of photon simulation algorithms, there is every chance that Stadia will get ray tracing using Vulkan Raytracing, even on the current Vega 10 GPUs that Stadia is currently using. Though as a pro-subscriber, I really which Stadia moves to the RDAN2.0 or CDNA based GPUs AMD will be releasing later this year.