Elixir.
The frontend world is gravitating more and more towards functional stuff, so let's go straight for the real thing. The actor based model of the VM should also greatly help to achieve concurrent/parallel/distributed stuff. Plus one could design awesome DSLs through Elixir macros.
But I guess everyone has at least one opinion why his/her fav language should be in.
The most interesting part would be (given that a BEAM VM runs natively in the browser/tab) what people would build with the power of linkable VMs. I'd be very curious!
