Ya I've actually seen a number a few shops making real moves in that direction, at least here in Vancouver. The OSS ecosystem is obviously pretty immature but I think it's getting good enough that it's starting to seem like a pretty viable option.
The only issue so far is that the libraries ecosystem is indeed quite young but that is natural.
Still, Ruby (even without Rails) is at the moment a more productive environment.
I really hope Ruby "3x3" [0] will be released soon enough and projects like Hanami [1] become production ready so that it can coexist in a complementary way rather than becoming replaceable.
[0] - https://blog.heroku.com/ruby-3-by-3
[1] - http://hanamirb.org