Peter Dimov via Boost
It's interesting that nobody considers the possibility that b2 is in fact a better build system than CMake, and consequently, that switching from b2 to CMake will actually make things _worse_ in some, if not many, respects.
That may be true, but if you took a vote among all the Boost users asking them which build system Boost should drop, I think it's pretty clear what the large majority's answer would be.
There's this axiomatic assumption that dropping b2 will automatically improve things, somehow, and I don't think it's true or warranted.
A less obvious benefit of dropping one of the two build systems is that it frees you up to potentially adopt a forward-looking build system (or rather build system + package manager toolchain). While supporting two build systems has its overheads, supporting three would be untenable. I guess another way of putting it, what substantial benefit does b2 provide to Boost that is not provided by CMake or could not be provided by another build system (that would also provide other substantial benefits)?