[xyzzyb]

Always be learning.

Don't learn Rails to make a career out of it (although that may end up happening!), learn Rails to expand your mental models.

And don't just learn Rails!

Learn Django. Learn Sinata. Learn Erlang-Web or Nitrogen. Learn Smalltalk. Learn TeX. Learn JavaScript (actual JavaScript). Learn Node.js. Learn Meteor.

Learning a language doesn't mean "ditching" anything. You're adding!

And one more thing: Ruby[sic] is far from the latest online fad. That would be JavaScript and Node. Rails was the latest online fad back in 2007.