I bet it wont be New York.
We have a governor who is all for it.
Our state Assembly has raised the issue and passed legislation.
But our Senate has killed gay marriage (and other GLBT leg) over and over again. The Dems just took control of the Senate this election, but already an anti-GLBT rights coalition has formed in the Democratic party. Malcolm Smith, who is going to be the majority leader, had his leadership challenged when four Democrats threatened to become Republicans because of Smith's stance on gay marriage, which would have left the Senate in GOP control. So, Smith gave them plum committee seats.
The state is such a mess that I doubt the issue will even be talked about in Albany (our pathetic little capital).
My bet, New Jersey. Ya, seriously.