Okay, I was already on the edge (hah), but the best ship is definitely Asumi and her senpai.
I just don't think the Mai ship could have anywhere near the payoff it is building up to.
Reading through the series, part of me kind of agrees with you. It does feel like there might be some signs that Asumi x Senpai might become a thing.
Not to mention the fact that Asumi and Mai don't know how much the other has changed. It's possible that once they meet up they'd find that neither is the girl they once loved.
That being said, I do still want Asumi to finally meet Mai again. And I'm not against a potential poly ending.