I feel like this won't necessarily happen with Rust, because Rust isn't locked down by any standard, breaking changes can happen and there are also Rust editions which help with the whole process of updating the language. The "better Rust" might just be another revised edition of Rust
Once you get those 10 year old legacy Rust projects that's when you'll be in a different situation.
There's also a potential paradigm changes (like OOP -> functional pattern) that require a complete redesign of the language, since incremental changes can only get you so far.
Python barely managed to pull of v2 to 3, so I guess the future is open to all options.
Basically you have to opt in your project to the new normal. All your projects dependencies can opt in, too, whenever they want to make the jump. Nobody has to opt in though.
Maybe C++ can do something similar eventually once modules are used everywhere. Those have a much cleaner separation of code between individual project parts than you can have with headers.
Change proposals that cause churn are regularly shot down.