Much as I'd like to switch to Elixir I see hardly any contracts calling for it right now. i.e. for every 300 or so Ruby gigs there'll be about 2 or 3 Elixir ones.

Ruby will never be Elixir or Erlang but if you can improve an existing thing why wouldn't you? Adding useful features from Elixir/Erlang to Ruby seems worthwhile, even if it doesn't get you all the benefits.

There will likely to be much work that won't be rewritten from scratch that would benefit and money to be made doing so.