Unfortunately we can't have a concrete answer on that before the end of the campaign. As much as we would love to have it, there's lots of factors contributing to the outcome as we're(The team) not the only one making the decision. On the bright side, we will be supporting mods so same-sex marriage will definitely exist in the game no matter what. Actually mods implementation might work even faster and better than our official implementation. :)
Last but not least, we had to go through lots of layers of approval before we can get it into the game so we're doing our best as well. We hope you understand that we're not against it but the process of getting it approved will take awhile.