I don't believe your claim about migrating to rust being untenable. Primarily because I worked at Google where I've seen them migrate the codebase consistently

I don't believe your claim about migrating to rust being untenable. Primarily because I worked at Google where I've seen them migrate the codebase consistently through years of development and language updates. If an enormous company like Google can switch CPU architectures, change their numeric types, change out their hash maps, etc, then yes you can migrate to using a whole new language. (If Google thought this was impossible, why bother with carbon?) I say this confidently because I've worked directly with people doing this and seen their work. I will claim one better and say: you can migrate to idiomatic rust (with help from some custom libraries) Should companies do this? Depends on the industry and the needs for the kind of safety rust provides