The Congress, whenever two thirds of both Houses shall deem it necessary, shall propose Amendments to this Constitution, or, on the Application of the Legislatures of two thirds of the several States, shall call a Convention for proposing Amendments, which, in either Case, shall be valid to all Intents and Purposes, as part of this Constitution, when ratified by the Legislatures of three fourths of the several States, or by Conventions in three fourths thereof, as the one or the other Mode of Ratification may be proposed by the Congress; Provided that no Amendment which may be made prior to the Year One thousand eight hundred and eight shall in any Manner affect the first and fourth Clauses in the Ninth Section of the first Article; and that no State, without its Consent, shall be deprived of its equal Suffrage in the Senate.
So, in order for an amendment banning gay marriage to pass, the following would have to happen:
For the measure to even be proposed, there would have to be,
A supermajority vote of "Yes" in the House of Representatives
and
A supermajority vote of "Yes" in the Senate
or
Application by a supermajority of all the various State Legislatures.
THEN a Constitutional Convention would have to be held, which would discuss whether this new amendment would "be valid to all Intents and Purposes" of the Constitution as it is framed, and THEN...
A supermajority of the various State Legislatures would have to ratify the Amendment
or
Conventions in a supermajority of the various State Legislatures would have to ratify the Amendment.
Given all of that, do YOU think it's likely this amendment would pass muster, let alone quickly?