I think it has to be more of a compiler driven movement. GCC and clang have to be the ones that accept to implement the standard of an alternative committee. Now I get this alternative committee doesn't exist yet, and there is no agreement of what the future could be (cpp2, cpp front, circle, carbon..) and it's a huge investment.
But developers will follow compiler. I sure would use circle if it was not a proprietary compiler.
Except the C++ compiler world is much bigger than two compilers.
clang is even lagging behind in ISO vs GCC, because most compiler vendors that fork it, mostly care about the backend, while two former major contributors are now are focused on their own LLVM based languages.
Which is why, those that care about portable code can at best use C++14 or C++17, while many libraries still target C++11.
So how do expect those two compilers to set the direction C++ should be?
Huh, I mean yeah gcc, clang and msvc, for desktop, servers and GP embedded hardware. That's like 99.99% of the compiling that most likely happen in the wild. Far from tunnel vision.
They are currently suffering from not having proper field experience on many features before setting them into the standard.