Using plugins from Rails and other frameworks with Elixir/Phoenix for auth, forums etc

Good point. So would maintaining different deployment setups include having to update the versions of Rails (or PHP etc) when new releases come out and sometimes update our own code to be compatible with the new release?

Do you think it would also mean that we need to have developers who know all the languages/frameworks so they can write code in each of them and/or fix bugs that arise in them?