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.
I don't have an opinion on the long-term viability of JS on the backend (though I enjoy Node.js for "realtime" web serving), but it wasn't clear from your post if you were aware that IO.js and Node.js are getting back together.
The io.js and node.js split is actually a sign of health in the core of Node.js. Tired of Joyent's stagnate stewardship, the top contributors forked it. They forced Joyent's hand into creating a foundation.
Now io.js and Node.js are "merging", but the merge is just the io.js codebase with some patches from node.js all under the node.js branding and the new node foundation (which has blessings from the linux foundation, IBM, Microsoft, etc). So the community has been "resolved."
