lua versions

Each Lua version compiles to its own bytecode, and the decompiler learns them one at a time, only once it can decompile that version as faithfully as the last. Today that's Luau.

dropping one that isn't read yet

You get a not-luau-bytecode error, which says which Lua the file looks like when it can tell, and costs nothing. The decompiler doesn't try to read it as something close, because a decompile from a misread file would be a different program that looks right.

When another version is added, it'll be in a release on the changelog.