I believe that Airi being the likely candidate for whose (full) route they might be going for shouldn't be a surprise. Always seemed like the most likely choice, and if the "footsteps in snow" narration segment is any indication, a glimpse from the future that they plan on bringing the story to, we have hopes of the anime actually offering closure on the relationship front.
I was actually surprised they so blatantly (from the perspective of a VN reader anyway) showcased the ending narration of Airi's route, along with the footsteps (though leaving the two people out themselves) - this scene and CG is one of the two that have remained stuck in my memory from the game. (The other being Miu in her catgirl attire handing out fliers
). So ... yeah, allowing myself to be cautiously optimistic about them actually heading for this closure, if they were bold enough to showcase it.
I keep wondering how they are going to integrate Miu's story though - as you noted, the OP contains a shot of Miu's mother, who only comes up when Shingo goes to visit her house, which suggests a lot of involvement with Miu. I am not sure how that is going to stitch together with Airi's main-route though, as Shingo can't be hanging around at Miu's clubroom and Airi's apartment at the same time.
Well, he can always start at Miu's clubroom and move on to Airi when on better terms with her, which I expect the anime to do, but my concern is that this leaves Miu
and Sana somewhat washed up. Shingo's and Miu's developing feelings for each other were a substantial part of her route after all, and more importantly - the main driving force behind Sana's excellent character development. As much as I liked Miu's route, I think the real treat of it was watching Sana behind the scenes - as she went from a man-hater (kinda) to someone who could accept them, to her own slowly developing feelings for Shingo.
Feelings she could never express and had to bottle up, both because of her realizing she doesn't stand a chance with his attention focused on Miu, and because doing so would have hurt Miu in turn, something she wouldn't do to her friend. I developed a lot of respect for Sana over the course of Miu's route, that's for sure.
But here comes the problem - Shingo and Miu probably won't get much on the romance front, in turn Sana won't get either, especially when Shingo starts hanging out at Airi's apartment, and thus the meatier part of Miu's route is gone, along with much of Sana's depth.
I guess what I am trying to say is, I am afraid that Miu and Sana are likely to be delegated to side-roles, more than anyone else, if Shingo focuses on Airi. And I would hate to see that happen, as I love both of their characters. Sakuno can always play an important part in Shingo's life, and Ange's antics can get away being largely unaffected either, but I feel like Miu's and Sana's potential developments largely depend on the time Shingo gets to spend with both of them in said clubroom. Time which I fear will be cut short with Airi as the focus.
Though perhaps I am crying prematurely, wouldn't be the first time I am wrong
The opening narration gives me hope we are heading for a definite closure, and if Miu's route has to be sacrificed in order to get there, so be it. Still, here's hoping they find a way to integrate the full depth of her story regardless. *twiddles thumbs nervously*.