What backend language will be the king of the next decade? Java, Ruby, Node.js, Python, C#/C++/.Net?

I have an open source project I want to start in this upcoming year, and have been questioning which back end language I should choose. I currently work with Node.js but have been wondering what its future will hold. I want to stay relevant, if the job market shifts. I actually have years of experience with Java and have wondered if moving that route would be a good idea. Or would Ruby be the route, where I should go?