For example, the current c++ project I work on (for a large company) has over 1.5 million lines of c++, spanning over 5,000 files, with business knowledge and bug fixes spanning over 30 years.
It's not going to get rewritten in anything else, and the same goes for large amounts of other business software.
The c++ will be staying c++.
I don’t say this out of any affinity for c++(check my other comments for details), rather because for business reasons, the core of this system will always be c++.
In fact we a currently embarking on a multi-million dollar project to upgrade the application to run in the cloud and one of our biggest challenges is finding qualified c++ candidates.
Despite that, due to the complexity and scope of the application and years of business knowledge captured in obscure parts of the code, there is no consideration for it to be rewritten in anything else.