Like other answers mention, senior developers will stay in high demand. Development still takes a very long time to learn, and I've read few indications that we are training people fast enough to keep up with the growing demand.
To be more specific, I would say that senior JavaScript developers are going to be a pretty darn safe bet. This is of course extreme confirmation bias speaking here (since I am one) but the graph below supports me with some kind of data. JavaScript is really easy to learn, but its extraordinary plasticity creates massive demand for people that knows how to build actual, well-structured apps with it, a demand that I strongly suspect will not even be close to being met in the coming years. Advanced JavaScript has not even reached academia properly yet.
Thanks to Donnie Berkholz on Twitter for the graph. (Sidenote: This graph has many serious statistical problems, but I consider the JavaScript bump so large that it cannot merely be a statistical anomaly.)
If I'm allowed to speculate more wildly, without data (because the language is so new) and outside of my own realm of development, I would say that the Mozilla Foundation-funded Rust (http://www.rust-lang.org) is a very strong contender as the new big system language, and one that many look upon as the possible successor to the seemingly immortal reign of C++. Many of the extremely senior C++ developers around me speak very highly of Rust, and they don't speak highly of many things, especially things that aim to replace C++. The language has been in development since 2009 - the spec has moved around like crazy the last few years, making it unfeasible for production development, but it's starting to stabilize and is scheduled to go 1.0 around March 2015. I suspect that it will be spraying rainbows.
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