Re: what if you 'outgrew' ".Not" (aka ".Net") itself?
I don't develop desktop applications (anymore), I don't run on Windows, and anything that's time critical (very rare - .NET core produces reasonable machine code) would be written in Rust, but only after the speed improvements are required and measured.
I grew out of C++ a decade ago, when my clients decided they no longer require desktop applications
I mourn the passing of desktop apps. In my own opinion there's something miserable about Web apps; they're slow, clunky, disregard local norms for keyboard short cuts and they also tend to be truly awful for people requiring accessibility help. The ultimate awfulness is the implementation of a pop-up dialogue box in html/JS/css; if you're creating dialogue boxes instead of just asking the local OS to pop one up for you, something has gone badly wrong, and coding has entered the realm of lunacy. Dialogue boxes like that are missing the whole point anyway; the use can't move them outside of the browser window to see what's underneath.
They're also wasteful of resources. A simple Hello World might require almost no html, but the several hundreds of megabytes of RAM needed by a modern browser to display that is absurd. Chrome especially.
I still write in C++, C (lots of real time stuff), but I'm realising that Rust is probably the place to go. It seems that Mozilla have accidentally brewed up a very good language. We're near the point where any new C++ project really, really ought to not use C++ but use Rust instead. There's simply nothing about C++ that makes it superior, whilst Rust also clears out all the nasties with memory.
The fact that Redox has got as far as it has with comparatively few developers in, what, 3 years I think shows that development in Rust can be quick.