Ruby on Rails is deflating like an overfilled balloon.
There is nothing wrong with the ruby language per se. It does a number of super neat things with its metaprogramming model and duck typing and mixins. The issue is with Rails which makes tradeoffs of performance over ease of programmability. Rails made itself a quick prototyping on-ramp for novice to intermediate-level developers but fancy metaprogramming has a cost of needing to manipulate and create large object models in memory on the fly and incurring a huge processing cost.
Ruby itself is plenty fast, especially with the new garbage collection model. To get that speed, though, the entire Rails framework has to be dumped into the dustbin and developers are forced to go back to standard models of development with threading models and direct optimized SQL queries. And it's not the rails way.
So that's a thing.
Modern architectural patterns require that servers reach the C10K model because hardware is not an infinite resource. As more customers get online and demand more out of servers, the programmability vs speed tradeoff is no longer an effective development model. Developers need systems that can reach the C10K model with a rails-like amount of fuss and development speed. Node.JS is a nice choice* but... it doesn't run on the JVM and the JVM gets developers there all the way from the outset.
Clojure, with ring and compojure, it's REPL environment and leiningen bootstrap environment for plug-ins, is awful close. It's fast. It's multi-threaded. It has LISP MACRO powers. It's also not like ruby at all unless one is really into lambda() functions. Then it is.
Scala, which brings the entire Java programming language with it, has Akka and Play Framework. It's also battle tested. Fast as hell. Feels like it is made to do heavy lifting. But much harder to get started and moving with coming from a Rails background -- it is much more like Java and Erlang had a baby than anything coming out of regular procedural programming.
Either way, Rails shops are going to need to consider going to one or the other. The hardware costs and the 99.999 uptimes and the customer needs combined with mobile will push shops off Rails and onto either Clojure or Scala just for the pure speed coming out of a jetty server. Combined with access to all the java libraries in existence, it's a ready made ecosystem. The question really is if the community will just fragment violently between the two or if it will pick one over the other.
* I like Node.JS. I really like Node.JS. I am finding I don't want to use it for heavy lifting. Why is this? I want to love node.js the same way I love python and take advantage of its web socket goodness but there's something weird. Maybe it's the community explosion that is making me go "not in the face!."