What is the third pokemon all about?

I was listening the other day to elixir wizards, a mostly elixir podcast, where Jose Valim was talking as a guest.

By the end of the podcast, he mentioned they were figuring out the evolution of Broadway.

If I get it right, Broadway is meant to be the evolution of something (it is unclear to me if it is supposed to be the evolution of Flow or Genstage).

He mentioned they were working on a new evolution of Broadway “figuring out what the third pokemon will be”.

It is my understanding that Broadway pretty much covers the ground for pipelines and parallel stages, so what is there to evolve?

What are the weakness they are trying to improve upon? Does anyone have an idea?