We saw Storm in the Cerebro sequence - wasn't she having her eyes examined? Probably a doctor trying to figure out why they're blue! But could show up as a young teenager in the sequel, provide a "youthful" view of the mutant/human conflict. Scott and Jean could as well. I'm guessing the kid with the dark glasses playing catch was Scott. The color of the shades is hard to determine, but I'm pretty sure the likeness was intended. Plus he was wearing a blue shirt with red and yellow details, I think. But there's nothing dating the first two movies... I'm pretty sure it wouldn't be that much of a stretch for the trio to be Charles' first set of "official" students. It's not something I feel is absolutely necessary in the sequel, and I'm not banking on it happening, but they could make for a nice contrast to the conflict between Magneto and Xavier. I'd love to see Magneto's twins - Erik trying to recruit his kids and them being conflicted because they long for a father, but also feel used by a man who's chosen his persuit of vengeance over them.