[tsally]

Depends on your timeframe. At the moment anything that runs on the JVM has a decent chance. There are certainly pure Ruby and Python shops that exist now. Hell, there's even a Common Lisp shop in Boston (ITA). However, you'll find it difficult to get away with not knowing Java and/or C++.

The next big thing in software is the same thing is was 15 years ago: knowing how to program well. This is no easy task. Focus on doing this and don't worry about the language. It's far easier to learn a new language than it is learning how to be a great programmer. For a starting point see: http://norvig.com/21-days.html.

(The only thing I would add to that is that knowing how to program parallel and concurrent programs is pretty important. Don't even go there until you've got the basics down though.)