Lua versioning is a really weird thing I'll give you that. I find class-based OOP a point against a language rather than for it, but there's already a huge chunk of languages that compile to/add types to Lua (https://github.com/hengestone/Lua-languages), with Wu and Amulet looking intriguing to me.
I'd also like a language that puts more emphasis on backwards-compatibility than Lua. Sure, everyone complains about the Python 2 => 3 transition, but there have been 3 new major versions of Lua since the release of Python 3.