Check it out, play with it, learn what the new ideas are about, but dont invest in it unless/until there's enough momentum behind it.
Right now for example, PHP would be a great language to pick up not because it's the newest of best, but because it has a large community, tons of documentation and tutorials, and we can be as certain as anything in life that it won't be going away any time soon.
To give another example, Swift is a new language from Apple that runs on OS X and Linux. There are a lot of people excited about the new features of the language, and wanting to use Swift for backend web frameworks. It might work great, but if you get stuck where do you look for help? Is there a large Swift community able to help you? Are there plentiful tutorials, walkthroughs, and documentation online? What if Apple decides to retire Swift development - would the community carry on development or would the language die without Apple's backing?
These are the sorts of questions that surround 'using a programming language' that have very little to do with the features of the language itself.