More or less furthering the gap we all knew was coming at one point or another (opinion from former Vim user but current Neovim user). Neovim ecosystem mostly write plugins in Lua by now, and most new Vim plugins will probably require something from Vim9 Script at one point.

If I had to guess: someone will eventually build a transpiler/converter of some sort, most likely vim9->Lua (assuming my guess that vim still has more users than Neovim).