I've been following Dawnguard infrequently, but every time I do catch up with what's trending as of late it has something to do with Serana, being unable to marry Serana, or wanting to be able to marry Serana.
http://www.change.org/petitions/bethesda-softworks-allow-serana-to-be-married
It has only been a week since this petition was started and its already acquired 2,500+ signatures. That in itself should speak volumes about what the community would like to be introduced in the next patch.
I'm beginning to wonder why Bethesda introduced such an alluring character that brought a whole new level of immersion to Skyrim only to tell gamers everywhere that this would be the one that got
away. If Beth was so kind as to give Serana endless amounts of unique dialogue, surely they could have substituted the stale, generic marriage dialogue with something unique.