I expected this answer at the top... JS will always be in demand for front end web positions (the MVC front end frameworks included), but as for the backend I have doubts about it's longevity, a major flag being the IO & Joyent split, as well as general back end developer anathema to using JavaScript I've sensed over the years (your's being an example). Maybe they'll resolve the community, and maybe greater numbers of back end devs will learn to enjoy JavaScript. It's hot right now of course, but thinking long term my experience tells me it's a risky choice if your goal is more pure back end dev.