I'd say it's safely over, the what if scenes are just that, what if.I'm giving the author more credit than you that they're not thinking fanservice is good narrative purpose. It's not good to show that three of the four girls results in a happy ending, as least as far as the metaphorical bedroom is concerned, nor is it needed. The arc dearth of scenes could have been filled with Ueno and Moka experimenting, which would be far more useful to the story.
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But we'll see one way or another with the next release.
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With the trio's characters concluded, all that's left is for Moka and Ueno to fix their intimacy and ride into the sunset.