Or not! Here in Toronto we've had a req open for a senior Ruby dev since like last October. We're seriously debating switching over to something else for no reason other than lack of available Ruby talent. Relatively view new devs are picking up Ruby nowadays. Job posting is here if anyone's interested --> https://angel.co/company/akira-2/jobs/106786-sr-full-stack-r...
My experience with ruby devs is that they are usually employed and not actively searching. Since it isn't the flavor of the week anymore you don't have as many programmers entering the field as ruby devs.
Mentoring is always a solid option too, the language and frameworks are simple. Any CS graduate worth his degree will pick it up in no time.