Unlike Tails and Shadow, I don’t see Amy Rose as the kind of character who can kickstart the narrative of a sequel on her own. She’d probably need to be paired with some other character or force in a post-credit scene, but the Sonic movies desperately need her after being a boy’s club for three movies. Amy is often treated as secondary to the main trio of Sonic, Tails, and Knuckles, but she’s ultimately a core part of the heroes’ dynamic and it’s about time she showed up. Paramount has omitted her for so long that I’m not sure how she’ll fit into this storyline, but someone over there needs to figure it out, and sooner rather than later.
If they wanted to get real bold, I could see Cream the Rabbit showing up alongside Amy, making the whole cast of anthropomorphic characters more well-rounded. Either way, I don’t see a version of events in which she shows up without Amy also being there, given the two are considered a pair not unlike Sonic and Tails. It wouldn’t be my ideal choice, but I can also see Paramount trying to package Amy, Cream, and Rouge as a girl-centric group in a call-back to the scrapped Sonic Heroes team that would have featured the three of them working together. I’d rather Paramount find a way to keep Rouge affiliated with Shadow, though. In any case, the Sonic movies need to add in Amy and I’m surprised they haven’t already.