It isn't litteral, it's a sort of teaser. It's put in perspective. So it's more like symbolism while at the same time representing what the next arc will be about. And I can clearly tell you that, if you had read arc 4, you'd realize how accurate it is. So nothing of that "trailer" is canon but it does represent the arc perfectly.
Why are people always searching for excuses for why he's into Emillia? I don't get it. Stop denying reality. He isn't into her because she looks like the witch. Hell, he couldn't even have known the witch back then. It's simply the worst possible logic that keeps reappearing again and again. Stop.