The economist in me wonders if marriage will someday be seen as a pre-Internet thing.
If you look at marriage the way an economist might, it is an exchange of services. Every marriage is different, but at its core you have two people who are choosing to provide one basket of services in return for a different basket. Traditionally (and historically), this means the man provided protection and financial stability while the woman provided children, care, and household management. In modern times, the picture is more smeared, but in all cases the parties are getting something while providing something, including the emotional benefits.
Marriage made sense when the world was inefficient. You married a person nearby who could provide most of your important needs while hoping your lesser needs could also somehow be met. It made perfect sense in the pre-Internet age.
But today you can arrange for any of your individual needs via Internet (Not very much in Rwanda). You can find lovers who don't want a commitment. You can find people willing to trade sex for travel experiences. You can find surrogates to have your baby, or you can adopt from another country. Then you can find a nanny who is willing to work primarily for room in your house. You can find an intellectual partner, a business partner, a sports partner, you name it. The Internet provides all.
For the first time in history it is feasible to create a virtual spouse comprised of a dozen separate relationships. And each would be optimized. Instead of dragging your spouse to a family gathering or football game, you go with someone who loves your hobbies as much as you do.
You might assume the virtual spouse doesn't give you the "soul mate" connection you seek. You can still have a special connection with people, but you don't have to drag that person to your activities. You can be in love with one person, enjoy activities with another, and find another who is a good listener. And the good listener might be putting up with you because you provide some other sort of benefit in return.
In other words, the Internet allows us to have a barter economy of relationships, as in I'll do this for you if you do that for me.
You might reject this line of thinking if you have a religious or romantic view of marriage. But I think economics always trumps those things in the long run.
With the current system, in which half of marriages end in divorce (again, statistics in Rwanda are not clear), you end up with tremendous economic disruption and hardship. With virtual marriages, you never have a big divorce with one person because your relationship is diversified. You could lose your massage therapist, your running partner and your "work spouse" all in one month without feeling especially sad about it.
Anticipating your objections, assume traditional marriage stays a popular option forever, but it moves from being the default arrangement to one of many options.
