We're pretty deep into using native erlang for our work so I don't know how much benefit we'd squeeze out of a switch to Elixir, but this is quite intriguing.
BTW, thanks so much for the mention. The core of Kazoo is an all Erlang Stack and we're proud of it (before anyone jumps at me FreeSWITCH is not written in Erlang but it's also not something we at 2600hz wrote). Building the sorts of massively scalable infrastructures we want with the uptime requirements we need would be much harder without the awesome concurrency tools Erlang provides.
Delighted that people care about these kinds of languages :D.
Disclaimer: I am the Community manager for http://www.2600hz.com and the Kazoo Product.