Switching from a monolithic framework like Rails to a number of independent communicating services that handle different responsibilities is a classic step in scaling. However, to the best of my knowledge that transition usually involves moving to a mostly-custom setup dependent on the app's specific needs.

It's not clear exactly what functionality Polyglot provides beyond, say, raw RabbitMQ, but if it can find a way to encode best practices in a service-oriented architecture it could be a handy tool for developers going through this process for the first time.