I read that std::dynarray was proposed in a draft for C++14 but was dropped out later on.
Are there any plans that this class will be included in future C++ standards, or has it been dropped for good?
No plans so far. The latest info is from this 2017 paper: https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0785r0.html
A custom header-only implementation from 2021 can be found here: https://github.com/cnbatch/dynarray
And good discussions: Why aren't variable-length arrays part of the C++ standard? https://stackoverflow.com/a/1887178/7471760