Still no threesome with Allison and Jeremy?
I agree with you and I think it also wouldn't fit Alison's Character espescially in a Scenario where she and Ian are a Thing in some way and therefore she is happy how it is going.Don't think Allison would like that.
It's clear she wants Ian and the whole Jeremy Hookup is just a pastime thing if Ian doesn't seem interested enough (yet).
I'm not a fan of this particular Threesome Scenario or in general of Jeremy in this Relationship at all but I still can see two Scenarios where a Threesome with them maybe could happen.
1) If Ian doesn't show any interest in Alison and she starts her Thing with Jeremy I can see her trying to start a threesome to finally come closer to Ian and kind of convince Ian from her in a weird way.
2) I could see some sort of "Chad" or "Asshole" Ian, who has a Thing with Alison and kind of dominating her, using her big affection (love) for him to convince her of nearly everything including a Threesome.