I need to get something off my chest.
Of course Stefan would still love her when she’s a vampire, love doesn’t just fade away, you guys. If you say it does, than you’ve never loved. The thing is, it wouldn’t be the same. He fell in love with Elena’s humanity, because she was the idealistic version of Katherine - good, selfless, HUMAN. Now she will remind him of the monster he think he is. Facts like that change the relationship, and not in a good way. He would love her, but would it be enough? That’s the whole point.