Ok then, everyone will just need to pay 3x as much for software. C and C++ will never return as mainstream UI languages for applications without extreme performance considerations because the cost of developing in such languages is too high. Before anyone gets their hopes up, I've written quite a bit of Rust and don't believe it changes this. Rust's type system is very difficult to teach and learn even compared to other complex type systems. Difficult to teach/learn = $$$. Even after writing a lot of Rust, I'm also still not very fast at writing it compared to my speed in other languages.

The only change we might see are more "native" UIs written in C#, Swift, etc. Also, Swift will not be a suitable replacement in its current form. Any replacement needs to at minimum work on MacOS plus Windows and by work I mean you can create a UI without crazy amounts of platform specific code.