[SPOILERS for anyone not caught up in the manga]
I have been having this thought and really wanted to see what other people's thoughts might be.
I have always been a ShirayukixObi fan, just gonna come clean about that right off the bat. The chemistry between the two, in my opinion, is above and beyond what's seen between Shirayuki and Zen. Also, the relationship with Zen very much has the feel of a first love, the shy timidness that comes with youth and inexperience. While that is all fine and good, in most cases, it doesn't make for a lasting relationship.
Now compare that to Shirayuki's interactions with Obi. They share a level of comfort and familiarity that comes from spending hours almost each and every day together, something that is impossible for Zen. A foundation like this makes for a long, lasting, and happy relationship. I am a firm believer in the idea that whoever you end up with should be your best friend (not to say you should marry your best friend, just that whoever you marry should be, if that makes sense).
I never really had any hope for them actually happening in the story. Shirayuki and Zen love each other and, while they will encounter trials along the way, they will end up living happily ever after. That seemed to be the kind of story this was.
Or, it did.
The idea of people in love always ending up together is very clearly squashed in the case of Kiki and Mitsuhide. There was so much build up of their relationship and a very obvious love between the two. And yet, Kiki puts duty before love.
Zen has made it clear that his duty to his kingdom always comes first. Always. If this were a story based in reality, I very much believe Shirayuki would end up with Obi. Alas, it is not.
Long story short, with the development of Kiki's upcoming nuptuals, I feel--rather foolishly--that there might just be hope for my ship. And this entire theory gets blown out of the water if something happend to Kiki's engagement and she does end up marrying Mitsuhide.