I'm all for some good old Rust evangelism, but I think it's a bit of a stretch to claim that KDE is "doomed"in the absence of a migration path to Rust, and it's not obvious to me that moving to Rust is somehow a necessity for the long-term viability of a project.

To your point about young devs and C/C++, afaik C is still pretty standard curriculum for CS degrees at most colleges and universities. C++ maybe not so much, but I would argue that it actually has a shallower learning curve than Rust. IMO the STL is a lot easier to get a grasp on as a newer developer than Rust's borrow checker or lifetime system.