But why? Storage is much cheaper today than it was in the 80s. While I myself don’t like huge Electron apps, trying to save every byte of storage is simply not worth it.
Many embedded systems hardly have any shell, and even when they do, it isn't bash (which isn't POSIX anyway), rather a tiny subset with the basic tooling for maintenance.
The POSIX shell is common, from the largest supercomputer down to the smallest ARM.
I don't think that there will be any new developments covering that full scope.