I've been around for a long time and I haven't seen a PL with this much momentum since Java was launched. Inertia is real, but the benefits over C++ are undeniable.
Bootstrapping seems a silly thing to be obsessed about as C++ will be around forever still, but it obviously can be bootstrapped if that becomes important.
Ada/SPARK already provided such benefits, and NVidia has chosen it instead of Rust for automotive firmware.
Rust momentum is meaningless for GPUs unless NVidia decides it gets to play in CUDA, and they are now one of the companies with more ISO C++ people on their payroll.
It is also meaningless for PlayStation, Nintendo and Xbox, unless the respective SDKs integrate Rust.
Bootstraping isn't silly, because LLVM and GCC are written in C++, so there isn't any "Rust will eclipse C+", when it depends on it for its existence.
SPARK doesn't provide the same feature set as Rust. If you want safe heap allocation in SPARK, then you get a garbage collector (unless you're talking really recent experimental extensions IIRC). If you want to forego the GC and remain memory-safe, then you also forego heap allocation. This might work for avionics code, but not for most apps.
Besides, the post you're replying to is talking about "momentum", and it's obvious in 2022 that Ada doesn't have the momentum that Rust does (however you define "momentum"). NVIDIA is not the entire industry.
Much of the rest of your post concerns video games, which are only a small portion of the total C++ code in existence. (And in any case it's not accurate to say that languages are "meaningless" unless the platform vendor officially supports them—console vendors don't maintain C# VMs either and yet Unity titles work just fine.)
What garbage collector? Ada never had one, besides the optional one in early standards, never implemented in any commercial compiler, thus removed in Ada 2012.
I wasn't the one asserting momentum, and can relate to plenty of other industries where Rust isn't even on the radar.
Going back to Ada example, Rust certainly doesn't have any momentum over Ada in high integrity computing.
Console vendors do happen to collaborate with Unity, and make it first party on their SDKs, so yet another lack of information.
Bootstrapping seems a silly thing to be obsessed about as C++ will be around forever still, but it obviously can be bootstrapped if that becomes important.