I think you're overestimating the likelihood that Tree-sitter is going to gain enough traction to be reliable for general purpose text editing. It's great for popular modern languages, but not for everything, and there's no fallback in Helix. I'm not convinced that's ever going to change.
Reliable? I trust Tree-Sitter's grammars a hundred times more than the underspecified regex monstrosities that power highlighting in other editors.
Tree-Sitter grammars are unit tested, have usable primitives for precedence and associativity, and are generally far more predictable than previous highlighting systems.
Also, name a language for which there is no Tree-Sitter grammar yet. The only remaining ones are so obscure that the missing "fallback" is irrelevant for 99% of users.
Python, Janet, Haskell, and Hare were the filetypes I remember either being unsupported or not working well. I need to be able to depend on basic language support from my text editor, even when I work with niche languages.
I've been using Python with tree-sitter on neovim for many months. It's great, and has a lot of improvements when compared with the old syntax system.
Re Hare: I haven't even set that one up. Setting up a new tree-sitter on neovim requires extra work for each tree-sitter, and that's definitely a flaw that needs to be addressed.
