Is the legalization of gay marriage in all 50 states inevitable?

Yes, because it would create too many legal problems not to. Currently if you are a same married couple in D.C. and you want a divorce. Your spouse could avoid alimony or child support by moving a couple of miles down the street to Virginia where it is not recognized, so they avoid payment. Also if you adopted a child in your same marriage and sued for visitation rights the other party could just move to a state where your rights aren't recognized. DOMA (Defense of Marriage Act) must be repealed because it's the 21st century's version of Jim Crow laws.