I think the coming generations will not "seriously engage in marriage" for the most part. Why should they? Our culture has told young women that marriage is bad for them, has no societal value other than as a social contract between two people, and exists solely to put women in a position subservient to men. It has also told young men that they are unnecessary except as sperm donors and cash cows for their ex-wives, and if they do stick around to try to help raise the kids, they can expect to be treated as clueless idiots, potential abusers and rapists, and little else.
There are still a lot of kids that grew up in the mid west with those fundamental values and other states that want marriage and children. They may do it differently but they will crave loyalty of love eventually even if it means several marriages.