He did not retire; he is still quite active and improving LuaJIT [1].
[1] https://github.com/LuaJIT/LuaJIT/tree/v2.1 [1] https://github.com/LuaJIT/LuaJIT/tree/v2.1https://www.freelists.org/post/luajit/Looking-for-new-LuaJIT...
It's more of an emeritus situation than anything, he's still active on the list as well.
I'd be ecstatic if hyperblock scheduling, or the quad-color garbage collector, were to drop onto the 2.1 trunk, but I'm not counting on it.