I think you might see some full-system rewrites for serverside components where Go will work out. But I think the projects we're talking about, like I said, have ended up in this position mostly because they can't easily be written in Go, or they already would have been (if only be a competitor).
My guess is what will happen in the cases where Rust is unworkable is that there will be less-secure forks for the obscure platforms.
F-Secure has been using TamaGo for bare metal on their secure USB keys.
MeadowLabs is using .NET with a tiny C++ hardware glue for IoT.
Aicas and PTC are still in business delivering real time bare metal Java stacks.
Astrobe is still in business selling Oberon compilers for embedded development.
MikroElektronika is still in business selling Pascal and Basic compilers for embedded development.
And then there are those 5 surviving Ada compiler vendors, one of them open source.
Finally, if there is no way around having to use C, there is no reason not to use C++ instead other that anti-C++ hater religion.
Unless we are talking about UNIX clones, thanks to them C will still be around for several decades to come anyway.
That sounds snarky, I know. I promise, I'm not being snarky, and, again: it ain't my first choice (it'll be fine though).
As for the other platforms, and what Google is paying for, lets see where the bribe drives people into, after all from your point of view Google should rewrite gVisor and everything k8s as well.
Yes it definitely will, but not only, specially among groups where not using a GC is more of a religious issue than an actual technical impediment.
Windows is a good example of this politics game actually.
Joe Duffy mentioned on his Rustconf keynote that even with the system running in production, the Windows team couldn't be argued against.
A system that even powered parts of Asian Bing infrastructure.
Likewise they clearly sabotaged the Longhorn efforts, to replace them with COM, and yet UWP, mostly written in C++, happens to usually run slower than traditional .NET applications on Win32, or any other compiled GC'd language on Windows for that matter.