I'm a front-end developer, not a back-end one. As I see parallel programming is a big word in the next years due to the rising of multi-cores and GPUs. We need languages for that, designed for concurrency and parallelism. Node.js is a small change on a single core but being more concurrent. There are more to be done. I see some languages shining:
Personally I would add Clojure too. But I guess the majority still have biases on Lisp family languages so it's less likely to be mainstream. Anyway this is just some advice from a front-end guy.