If people actually got to make their own choice on that I'd strongly guess that Flash wouldn't have ever gone away. Browsers declared HTML5 was going to replace Flash long before it was actually capable of doing so (and arguably still isn't).
But it only took ~4 "deciders" to kill Flash regardless of what anyone else wanted, which was Apple, Microsoft, Google, and Mozilla (and eventually Adobe decided it didn't care about Flash anymore either). Nobody so centrally "owns" C++ such that there could be a concerted deprecation effort that anyone would actually care to listen to & respect. Even if the C++ committee itself decided to kill C++, and got G++, MSVC, and Clang on board, which is extremely unlikely, would anyone even care that much or just keep using the last release of the compilers with support until the end of time? Kinda like they do for FORTRAN. And COBOL. And etc...
But it only took ~4 "deciders" to kill Flash regardless of what anyone else wanted, which was Apple, Microsoft, Google, and Mozilla (and eventually Adobe decided it didn't care about Flash anymore either). Nobody so centrally "owns" C++ such that there could be a concerted deprecation effort that anyone would actually care to listen to & respect. Even if the C++ committee itself decided to kill C++, and got G++, MSVC, and Clang on board, which is extremely unlikely, would anyone even care that much or just keep using the last release of the compilers with support until the end of time? Kinda like they do for FORTRAN. And COBOL. And etc...