But no, there is no mention at all. I guess it's a good thing that they just rolled the "it's time to move on" ending in with the same group that told him to persevere. Everybody gets a happy ending with the romance that way, and they did leave it wide open for pretty much any head canon you could want...right down to being able to believe that Cass helped them overcome the addiction while still allowing them to use their abilities...essentially becoming Seekers. Of course, that all depends on what happened to Cass as well - in my game she rebuilt the Seekers, and does spend time in the DLC talking about how she had to be selective as to who she allowed back in. I will believe that Rhiannon no longer needs lyrium for her abilities...til Bioware says otherwise. I really can't picture a clean Cullen being with someone who is still using...so that's how I'll roll with that one.
Bioware could have been very nasty to us with it too. They could have had him die from withdrawls, or show them losing their memories. But nope, happy ending! I feel good about it.
I was kinda apprehensive at first about the marriage thing because I personally don't believe that folks need to get married to commit. BUT they did handle it well...and his proposal was precious. I did try out the "no" response and I didn't like it. They didn't handle that one well, in my opinion. It just gets way too uncomfortable. She starts fidgeting and says she doesn't believe in needing a ceremony and you can almost see the disappointment on his face for a split second before he comes back and says they'll be together no matter what. To me, when someone doesn't believe in marriage and is in a serious relationship, that sort of stuff has already come up...so the other party wouldn't even ask. My b/f would never ask because he already knows the answer. In this case, it just kinda played out like one of the instances that always spells the doom of a relationship when someone says "no" even if the person follows up with "but I still love you." They hug and that's it - end scene. I reloaded and went back and said "yes." It was very cute and I can totally picture Rhiannon saying yes. And even better, the slide with the fur-baby in the end was the icing on the cake. They can totally be the awesome auntie and uncle to Mia's kids. So...as a non-marriage child-free person IRL...this was AWESOME and I was SO VERY HAPPY with the outcome because Bioware made it work for everybody. YAY FOR EVERYBODY!
I also picture all the uproar when folks find out they tied the knot in secret. In the beginning when Josie was telling Cullen about all the proposals I was picturing some big scene where they would have to deal with political arrangements coming in for the both of them.