There's a high chance they won't end up together. Tho, Hestia loves Bell so much, to the point we perceive it as "romantic" it's really just more of her caring so much for her child. Bell loves Hestia, that's true. But not romantically. He loves her as a family just as everyone else in the Familia.
Ais has a high chance of ending up with him since there are hints which she appears to slowly develop feelings for him. If you didn't notice, Ais character development has slowly been developing because of Bell. From a stoic airhead, to someone who's slowly beginning to change her personality. Even Loki and the 2 girls in their Familia has noticed this. Before she used to hate monsters and didn't listen to reason. But because of Bell's words and Weine, her perspective and understanding changed. Even if they fight and/or have misunderstandings, in the end, they still make up and get along with each other. Bell is basically the source of Ais' character development.
That said, there are still pretty much other girls who are really good and unique in their own way. We'll see who the author decides. Knowing Hestia, she'll always respect who Bell will choose tho she will act like a tsundere about it.
