Change your shell now and test - no need to wait.

    chsh -s /bin/zsh

 - All the scripts that depend on `bash` syntax will still find and call bash. 
 - the same bash from Mojave is shipping on Catalina and migrated users keep their old shell. 
 - Many blogs have great write-ups on moving preference files - here is one such - https://scriptingosx.com/2019/06/moving-to-zsh-part-2-configuration-files/
 - [Armin turned his blog series into a proper book][1] with about 22k words. 

 - - -

Also, I would estimate 95% of macOS users don't use a command line and of those that do, another 95% won't have to change anything significant or at all. _(I'd wager it's more like 10% of the 1% that know shells exist need to do anything other than port a couple lines in their .dot files)_

Your prompt will change and if you changed your prompt on `bash`, the way to change it on `zsh` is no harder and no less documented than bash.

The newer shells would fail to ever get off the ground if they broke major items or caused a painful adaptation period. If you want a more fundamental change and really want a shell you need to think about and requires training and intention to adopt - try [fish][2].


  [1]: https://books.apple.com/book/moving-to-zsh/id1483591353?mt=11&app=itunes&at=1001lpyX
  [2]: https://fishshell.com