We do! Celluloid (the actor model) is vastly superior to EventMachine in my opinion. It fits much better to Ruby's OOP style and I suspect would integrate into Rails very cleanly. I am positive that bringing any EventMachine technology into the Rails stack would be a mistake.
I am saying that with a bit of a bias as I have written my own celluloid-websocket[0] gem that comes with a Rack adapter. But I wrote it because I put a project using EventMachine websockets into production and was not happy with it. Now in a new project I can just hook up the celluloid-websockets Rack app and run it using `passenger start` or any of the Rack application servers.
Even though so many people seem to flock to Node.JS for these kinds of servers, the fact that as a language Ruby is superior to Javascript remains, even if Javascript VMs are a hundred times as fast. As long as Node.JS is run on standards compliant VM's things like promises are just lipstick on the callback hell pig. You can write clean and understandable Ruby to solve any problem, including Websocket servers. We as the Ruby community were just late to the asynchronous I/O party. Now Celluloid is production ready, there's really no reason (except for performance of course) for a Ruby developer to write Javascript on the server side.
(sorry for my extreme opinions, if you want a more nuanced deliberation on a point just ask ;))