The .NET framework[0] is always useful and I think it's here to stay for a long while. You'd be able to write mobile apps using Xamarin or business apps for Windows. Also apps for the new Ubuntu mobile OS will be possible.

Personally I find Go[1] interesting and it's something I'm hoping to pick up in the coming year. It seems like a fun language, well suited for building web services that handle lots of traffic.

Lua[2] might also be nice to learn. It's used for scripting in a lot of games. For example: in World of Warcraft you can create your own Lua add-ons. Lua can be easily integrated into your own apps / games, since it's just a small C library. It might be a good language to learn if gaming interests you, since lots of games make use of Lua in some way.

And as someone else already mentioned in this thread: functional programming will become bigger in the future. You can use the functional programming style with .NET if you choose to learn the F# language.

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[0]: http://en.wikipedia.org/wiki/.NET_Framework

[1]: http://en.wikipedia.org/wiki/Go_(programming_language)

[2]: http://en.wikipedia.org/wiki/Lua_(programming_language)