While I don’t have much experience with Ember yet, just working with clients who want a richer more responsive experience on the web I can tell that knowing Ember is going to make your job way easier. I found this post today from The Frontside which talks about the future of the web:
I can’t actually predict the future, but I can bet on it. And Charles and I are betting The Frontside’s future on the fact that Ember provides a foundation for creating amazing, next-generation user experiences for the web.
And they talk about the downside to using Server-side MVC frameworks:
What server-side MVC frameworks are not particularly well-suited to are user-driven, stateful UIs like you’d see in desktop apps like Word, Excel, or iTunes.
It’s a great read and if you want to be a relevant web developer in a few years I suggest you checkout this article and start learning a front-end framework.