I'm a ruby & rails developer, and I love them both as well. They're good for a lot of things and are generally enjoyable to work with. My side project is a rails app and I wouldn't have it any other way. I think you'll find the day that ruby isn't needed or used anymore is far, far away. php is still around, as is java and perl. As long as developers go to it and use it, it'll still be used. And rails is still one of the top web frameworks out there.<p>Javascript would be a good bet. that's what I have been meaning to focus on as well. It compliments rails development, and opens the door to other JS frameworks that you may or may not use, and other things like node or even unity.<p>And by extension, learning those front-end frameworks (like angular) would be good too. Some shops that run rails have something like that in the front end. But knowing JS makes those frameworks more approachable regardless.<p>JS frameworks, single page apps... they're a way to go, but they aren't replacing rails by any measure. Just more options for implementation, which is whats great about the web. But in the end it's just another way to build a site. Worth mentioning is that there have been some high profile shops that tried to go fully embrace that idea (everything in the front end) but ended up reverting back to server rendering and sprinkling with JS.<p>Go is great if you've got google level problems, but I wouldn't want to write code in that unless I had an actual need that played to Go's strengths. If i can do it with ruby, i totally will.<p>So, I'd say ruby and ruby on rails are still good bets, especially if you're trying to build something yourself. But it's really up to you and your priorities and what you're willing to bend on. You could learn .net and php and do work for shops that use them in their codebase, and that's a way to go. You could learn objective-c and write apps for iOS. It's really a matter of what you want to do, what tools exist for doing that, and which one you prefer.<p>Coming from perl and php, i have never loved anything the way i love ruby and ruby on rails. It was well worth the years it took me to understand and master them both, and the associated knowledge (testing,html5,css3,etc). It's hard for me to see myself using anything else.