Is there a framework for writing asynchronous servers with Lua?
Much of the complexity comes from error handling, not just the async IO. Erlang gets that right, too. I don't know how much error handling node.js does. (I plan on checking it out eventually, since my framework will be compared to it.)
I don't have a time frame yet. I'm also working on a compiler and a bunch of other stuff, and I'm really not a web developer, so it's been a fairly low priority.
If you're not worried about being "web scale", it's not hard to write an async socket server using luasocket's sockets for nonblocking TCP IO and luasocket.select for scanning for active connections. It gets bogged down once you have > 100 or so idle connections (the usual trade-offs with select apply), but it's easy to write, very portable, and (on x86) LuaJIT is amazingly fast. Contact me if you want example code.
I've been working on an actual framework for async servers (libev-based), but haven't had much free time lately.