The only semi-realistic way I can see Bash becoming mostly obsolete is with a tool that provides automated migration of large scripts, and the only project I know of that's even attempting that is Oil: https://www.oilshell.org/

But for spawning a command in a subprocess, there really ought to be a standard OS API that doesn't involve invoking a shell at all. I expect that most or all implementations of posix_spawn and execve don't invoke a shell, but the standard call to start a process on Windows, CreateProcess, apparently does involve cmd.exe for some bizarre reason, and that's why this is a problem in the first place.