[Beltalowda]

> This will give vimscript a Python 3 moment

Not really; the Python 3 problems were due to incompatibilities in the APIs (e.g. functions returning str previously now returning bytes) that couldn't be automatically converted, not merely due to "being incompatible".

You can safely mix VimScript and Vim9Script; you can even use both in the same file. It's not a problem. I wish people would stop using "Python 3!" on any incompatible change; the details on what is incompatible really do matter.

> I wish he’d have embraced Lua like Neovim

Vim has supported Lua since 2010, and Lua doesn't exactly have the best story on compatibility by the way.

[dvogel]

This is all correct. To quote from the official description of vim9script:

    Vim9 script and legacy Vim script can be mixed.  There is no requirement to
    rewrite old scripts, they keep working as before.  You may want to use a few
    :def functions for code that needs to be fast.

So entirely the opposite of the python3 split.