Not really, there are two limitations that no one is contesting in regards to marriage, and sexual relations in general for that matter.
-Both participants must be consenting. Aside from the obvious, this principle alone bans children, animals, and other such things.
-Participants must not be closely related. This principle is likely to remain enforced indefinitely, as there are strong biological and psychological reasons to keep incest illegal.
The main reason that gay marriage is now being contested is that unlike the above two items, there is no strong ethical argument against it, just ages old prejudice.