So I take it you don't believe any of these languages are going to achieve much traction in the business world. That's generally my take too. But there's still a lingering doubt: what if one of these is the "next big thing"? Just like you would have kicked yourself if you had had the opportunity to buy Google shares when they had not yet passed $10.
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.)