Could something like this happen here?
From the New York Times:
Some are divorced and disenchanted with marriage; others are young couples ideologically opposed to marriage, but eager to lighten their tax burdens. Many are lovers not quite ready for old-fashioned matrimony.
Whatever their reasons, and they vary widely, French couples are increasingly shunning traditional marriages and opting instead for civil unions, to the point that there are now two civil unions for every three marriages.
When France created its system of civil unions in 1999, it was heralded as a revolution in gay rights, a relationship almost like marriage, but not quite. No one, though, anticipated how many couples would make use of the new law. Nor was it predicted that by 2009, the overwhelming majority of civil unions would be between straight couples.
It remains unclear whether the idea of a civil union, called a pacte civil de solidarité, or PACS, has responded to a shift in social attitudes or caused one. But it has proved remarkably well suited to France and its particularities about marriage, divorce, religion and taxes — and it can be dissolved with just a registered letter.