It seems to me that the “mainline” GOP is being pulled by two forces here:
1) Infiltration of social liberals
2) Prognosticators telling them that gay marriage is an inevitable reality - whether now, or under a liberal majority Supreme Court down the road.
So, there are the true believers, and the politicos who want to harvest votes at any cost. And if they believe the public attitude is eventually going to make this issue “no big deal”, then we’re going to see more and more of these recommendations. The schism has already begun however.
Based on trend lines and generational breakdown of poll results (obviously, younger voters are going to stay around longer than older ones, Chicago Democrats notwithstanding), they may be right....