The state may call marriage what it will; that redefined marriage may become the law of the land; popular consensus may absorb a vaguer set of definitions of marriage; but I will never call something marriage that God does not.
God is the Person who created marriage, designed marriage with certain precise components and parameters, and gave us this loving gift for our joy and benefit. To our shame we sometimes forget that its ultimate purpose is for His glory and praise.
So we go into our future, two sorts of marriages diverging, two paths splitting and moving away in opposite directions. The one marriage is secular, human-engineered, temporal, with relative and changing definitions. Societally driven, government-enforced, and defensively hypersensitive to criticism.
The other is a gift from the Creator of the Universe, unchanging, supernatural, mysterious…and eternal. It is not fragile, and it will never disappear.
No redefinition, no legislation can touch real marriage. It will always be what it is, even though no one at all should be left to embrace it.