The vote was 338 nays - 303 ayes. Had the ayes had it, the matter would have been put to the Presbyteries for a vote on whether to make it the law of the PC(USA).
But the climate for a same-sex marriage vote could be on the activists' side in the future. During deliberations and several votes on different versions of marriage proposals on Thursday, younger members of the church expressed support for same-sex marriage much more strongly than the church's older members. Church surveys also show an increasingly pro-same-sex marriage stance as the younger Presbyterians gain more leadership positions.
-from a 7/6/2012 article in the Huffington Post.
I would suggest that "the climate for a same-sex marriage vote could be on the activists' side in the future" because between now and the next GA in two years plenty of the opposition churches will have left.