You're totally right the frameworks come and go, but on the other hand they come for a reason. And when I am learning a new framework there's usually something

You're totally right the frameworks come and go, but on the other hand they come for a reason. And when I am learning a new framework there's usually something more I gain than just something to put in my CV. For example when I started with Spring I learned a whole lot of IoC and AOP. It was quite long time ago, but the principles that stand behind a framework might be very influential in the long term. I like the Scala suggestion, because the last time I was involved with functional programming, I was using Haskell which I found quite difficult to grasp to a level that's useful for real-world projects.