C++ has been doing a new version every 3 years: 11, 14, 17, 20, 23, now 26. It's a good amount of time to get people on board, implement features in major compilers, experiment with them and do some feedback cycles before finalization. I greatly prefer this to Python's rolling releases where the compatibility window is constantly shifting.
And rust isn't going to replace C++. Languages don't really die on a timescale that matters to the people working on the C++ spec. By the time C++ is truly dead, rust will be soon to follow.
What happened to C++24 and C++25 ? /s
I think rust will replace C and C++ if they will resist making incompatible changes every couple of years.