I am not sure what you mean with production-ready here.

Erlang has certainly been used in production, not only Whatsapp but also have a lot of production systems in telecom where requirements on up-times etc are pretty high.

If you mean that there are no ready made off-the-shelf standard way to handle runtime configuration and deployment I guess it is because the big telcom products usually roll their own per product so it haven't made it into the OTP backlog.