This is exactly what several flavors of secular humanism have tried, but it turns out, without the cultural and memetic stickyness, these things don't become popular. You can have a personal ethical system without a pretend religion. I don't see how this is in within anyone's interest or time. That said, I've seen things like a very liberal interpretation of buddhism take this kind of role. Mostly, it seems, for the benefits of meditation, but this is a small movement. I'm not sure where millenials will fit into all this, but they are even less religiously affiliated than gen-x, which is a good sign, imo.

Personally, if I had a choice, I'd love to see things go towards a more decentralized role (personal and private spirituality) than yet another centralized role like organized religion, even if some new "ethical" religion takes over. I do sometime fantasize about some new spiritualism that's outcome based, but once more than x amount of people are involved, then politics takes over and any ethical integrity is lost.

As a recent dad, I have found no real replacement for all the religious holidays part of my culture. How do you replace Christmas? How do you handle relatives asking when you will baptize your baby? My non-religious wife and I take a hybrid role where we'll celebrate certain things for the sake of family, but won't do others like baptism. I think shopping around for one of the more 'less religious' religions is just a waste of our time and a disservice to our kids. I'd rather teach my kids the history, criticism, and the folly of organized religion than shove them into one my liberal values will tolerate. Dragging them to a Universal Unitarian service just seems to be kicking the can down the road.