In connection to Mike Pall's comments on the status of v3.0 made last November, I would like to mention this post [1] of his, back in 2017. Mike Pall had proposed replacing LuaJIT’s 64-bit NaN-tagging with a variable-sized slot design to support larger pointers and unboxed value types. Also translating source directly to executable SSA form, without bytecode generation. Such changes might be part of the complete architecture change under consideration for v3.0.
[1] https://www.freelists.org/post/luajit/Few-questions-about-Lu...