I think the new C++ tooling will be in the ballpark in much the same way that Java 8 is in the same ballpark as Scala and remove much of the impetus for moving

I think the new C++ tooling will be in the ballpark in much the same way that Java 8 is in the same ballpark as Scala and remove much of the impetus for moving to Rust from C++. I think that you extrapolate from an incorrect analogy. Java is a relatively simple language (except the mess introduced by generics through type erasure), that is mostly understood by regular practitioners. Java suffered far more from the lack of modern language features than technical debt. Consequently, it benefitted from language extensions tried first in Pizza/Scala, etc. C++, on the other hand, is a very complex language as a result of inheriting C, the lack of deprecation of misfeatures for compatibility, and perhaps questionable design choices. C++ suffers not so much the lack of language features (though support for real algebraic data types and modules would be nice), but from complexity. Complexity of the language can only be reduced by breaking compatibility.