As Vim9 comes alive, and Neovim community focuses on Lua plugins instead, it seems this release is finally the update that will put a hard branch on the two communities. Up until now, most plugins (except Lua-only ones of course) have worked in both editors, but it doesn't seem like Vim9 will be supported in Neovim, so I guess what people go with now, will decide what you might stick with in the future (unless you're eager to switch development environments).