I don't think they need to. They might if they have some particular need in it, but there are way more interesting things to learn if you are interested in something new, like Rust of example.
While C++ has a place in the .NET ecosystem, there is a reason that C++ and .NET are different beasts and still exist side by side as different universes. CoD and Photoshop are C++, they would probably benefit from being Rust applications.
While in the past you would be well prepared if you knew (say), Haskell, C and Python, a good lineup in the future could be e.g. F# and Rust instead.
Is C++ broken? I'd say with the C++11 and C++14 changes, it's getting less and less "broken" from the complaints usually levied at it.