Why is linux supporting taking a while? I figured the underlying graphics subsystem on Android is Vulcan right? Wouldn't that also be the main graphics subsystem on Linux these days?
Testing/Validation and bugfixing. Just having Vulkan isn't enough to enable it by default, everything actually has to work right. Even for Android this is only for specific types of devices. You should be able to force enable it on Linux right now though. It's just not GA quality guaranteed.
Similar. I've done experiments with subgroups suggesting approximately a 2.5x speedup for sorting (using the WLMS technique of Onesweep). Binding arrays will be very helpful for rendering images in the compute shader. A caveat is that descriptor indexing is not supported on mid-old phones like Pixel 4, but it is on Pixel 6. I somewhat doubt device buffer address will be supported, as I think the security aspect is complicated (it resembles a raw pointer), but it's possible they'll figure out how to do it.
Not really, that is not the problem of WebGPU. The worst you can do is crash the tab. With an unstable graphics driver, there might even be the option to crash the system but that's hardly a security issue, only an annoyance.
Historically any time an attack surface as big as WebGPU has been exposed, "the worst you can do is crash the tab" has not ever been true.
Also note that for an unstable graphics driver, the way you usually crash the system is by touching memory you shouldn't (through the rendering API), which is definitely something that could be exploited by an attacker. It could also corrupt pages that later get flushed to disk and destroy data instead of just annoy you.
Though I am skeptical as to whether it would happen, security researchers have previously come up with some truly incredible browser exploit chains in the past, so I'm not writing it off.
WebGL has been around for more than a decade and didn't turn out to be a security issue, other than occasionally crashing tabs. Neither will WebGPU be.