Exactly. The Constitution is intended to delineate what the government can do. When it is silent on a topic the Government has no authority. I would go so far as to say where an amendment restricts or abridges an individual right it would be contrary to the Constitution. The 9th&10th amendments seem to clarify and restrict the scope for all of the Constitution, past and future.
But the overturning of proposition 8 in California is probably a bellwether. A government-defined institution of marriage is going to be subject to the premise of equal protection and to limits of government powers and authorities.
Probably will be. But helping further that log down the flue is something we shouldn’t do in any way possible. It would still blow if the states adopted gay whatever freely. But it would at least be constitutional.