Marriage will be replaced by an annual contract (holierthanthou)
I think we will certainly see some weaker froms of marriage that are designed to last a decade or two rather than a whole life time, but traditional marriage will still be an option. Increasing longevity is the key - if you marry at 20 ang live to well over 100, that is far too long a commitment. People will want marriages that aren't necessarily forever, but don't bankrupt them when they end