Bash has been available via the likes of cygwin or mingw builds for years; but the Linux subsytem may simplify things (...wait, this is still Microsoft we're talking about?).
Does anyone remember the original POSIX subsystem that came with Windows NT?
That was a _minimal_ POSIX subsystem which satisfied US Gov requirements intended to u/g their UNIX systems. Unfortunately they didn't specify a level of POSIX requirement, so MS added the minimal qualifying support and undercut the Big Iron UNIX vendors. Queue lots of unhappy end users presented with systems which wouldn't run their existing code...