Even if C++ is irrelevant for new code, there's so much software already written in it that we'll be maintaining it for decades to come. I'd argue that Cobol and Fortran have been mostly obsolete for new code for almost 30 years now, yet both are still widely used today, and they've even had major updates in the past decade [0] [1]. And there's even more software written in C++ than there is in Cobol or Fortran, so I don't think that C++ is going away any time soon.

[0]: https://en.wikipedia.org/wiki/COBOL#COBOL_2023

[1]: https://en.wikipedia.org/wiki/Fortran#Fortran_2023