If by "niche" you mean "anywhere code has to run fast or in a small space." C++ is displacing C in embedded applications. The JIT compilers in Java and MS CLR are in C++. C++ is only growing for use in simulations, which remains a rapidly growing field.
C++ remains a good choice for GUI development, which is hardly niche.
This is progress - it used to be that the majority of programs had to consider processor and memory utilization as a primary concern.
The examples you gave are excellent examples of where it makes sense to use C++, but that's not what the majority of programming is now.
It's naturally de-emphasized in the web world, but there's still a huge amount of C++ being written. Most desktop and a large percentage of systems, mobile, scientific and embedded code is written C++. There's just relatively little cross-pollination between those worlds and the web world.