You should definitely keep an eye on Val and Carbon. They're being designed to be interoperable with C++. Both are designed to match C++'s performance while still being able to work with your existing C++ code. Both of these languages offer a more modern developer experience and are built with software and language evolution in mind. They have practical safety and testing mechanisms, etc. Definitely check them out if you're looking for a C++ replacement!
https://github.com/val-lang
https://github.com/carbon-language