No, that is not planned for direct inclusion in stdsimd.
Using dynamic feature detection has a small cost each time you check and then branch to one code path or the other.
Most operations within stdsimd are simply too small to justify that cost being a part of every function or method call.
Accordingly, the stdsimd crate only uses compiletime feature detection.
We suggest that you try using the multiversion crate in combination with stdsimd if you want to benefit from runtime feature detection.
Because the functions and methods in stdsimd are marked #[inline], the actual code generation is performed in the using crate.
In other words, stdsimd should combine with multiversion just as well as any other Rust code does, and correctly benefit from function multiversioning.
If you do find specific examples to the contrary, please report them to our issue tracker.