Rails didn't hit that wall. Neither will Ember. FYI Ember is introducing new ideas by the second (pods, composable components, components over controllers, DDAU, etc) but the community eagerly awaits and embraces them. I don't know why that is.
This is really a fantastic point. It's sometimes as if people think these type of projects exist in isolation and any perceived flaws are permanent. They often fail to appreciate how much the flaws will invoke a response to address them, making them better than they would have been had the flaws never been strongly felt by the community in the first place.