I have to correct a few other things in his post.
a) There are shittons of frameworks for Ruby. Rails is definitely not the only one, its just most popular. Most good libraries are framework indepenedent and have plugins into that framework. One example is Guard or CarrierWave. The elegance of it all is what separates it from java.
b) Much easier and faster to develop for. allows for rapid prototyping and mutations. Writing front-end servers in ruby > writing front-end servers in java as ruby can do things in 1 line that take 50 in java.
c) As we see with facebook, sometimes a "slow" front-end written in a prototyping language is better, but the back-end is written in a performant language.
d) The power of ruby/rails is the community. That is it's number one source of power and without it, rails is crap. There is a lot of Java developers, yet the awesome java frameworks are things like hadoop, meant for data processing.
I don't think there will be a "second coming" of java. I think Java will die, but the JVM (will probably) live on. Either that or the JVM will die to be replaced by something the community makes, if oracle has any say in the matter, knowing how oracle is doing everything possible to alienate java.
However there will be no second coming of java because it never left. Java is still going strong within the rails community as most are fully aware that you write your application in ruby, and anything important that has to be performant will be written in java. There's just no alternative.