Well, Aerie becoming Minsc's new witch is only one version of canon, haha. In another, she runs off with Haer'Daelis. As for a tougher, more mature version of her, we do get to see that already, in Throne of Bhaal.
As for more friends coming back....ehhhh....the ones Larian has had so far have been kind of a mixed bag. (Though I'm not upset with some of their choices as other people seem to be.) Personally, I'd love to see Jan Jansen, or a descendant of Jan Jansen, being included as a companion. Give us a shorty companion!
It'll usually happens since she's likely to be the first new companion you come across in BG2 (excepting Yoshimo of course), and if you let the romance with Haer'Dalis play out she ends up dumping him. I tend them to imagine them now all going around in a big campground scenario like in BG3 and travelling together at various times. And obviously there's been an additional century of her battling slavers and finding Faenya-Dail, then realizing the Avariel are actually just really boring; she could be like a quippy action hero. Or you could potentially just go full Autistic Pixie Dreamgirl™. But yeah a Jansen or a Fentan or descendants of other characters would be really neat to see too. Ooh; maybe Korgan cleaned up his act and won Mazzy over
