LÖVE

I'll bet on a new GC within 5 years, but none of the big users of LuaJIT have any reason to add 5.3 support.

My amateur perspective: Lua 5.1 is practically complete to me. It has all the features I'll ever want. The only thing that is needed is more speed and LuaJIT is a godsend.

My opinion is that, at present, LuaJIT is the fastest scripting language in the world. Lua is simply not that fast.

Maybe in some years, if LuaJIT has effectively stagnated, it'll make sense to go back to Vanilla (which maybe will be faster then). But right now, I think the decision to move to LuaJIT was the correct one, and I think we should stay with it at least for a while. That said, it doesn't hurt to keep the code "reasonably ready for the change". For example, by not using LuaJIT's FFI, or using it only in a single place with an abstraction layer on top - that kind of thing.

Definitely. The speed difference between Lua and LuaJIT is pretty darn big. I wouldn't go back. I wouldn't want to go back. Hopefully someone picks up JIT and keeps it going. It'd be a shame for it to get abandoned or left on a shelf because the dev was bored of it and didn't want to give it to a new dev.