Gohan has more hidden potential, yes, but without getting mad, he's not stronger than Vegeta in the Buu saga. And when Gohan went SSJ2, if Vegeta couldn't I'm sure he'd have made a comment either pointing that out. But, at the same time, he could've made a comment saying he was a SSJ2. I just have reason to believe he reached the form because he's always training & has always been known to become stronger. But, as you've said, there is no true answer as Akira Toriyama didn't let us know what was what.
There was already a movie made after GT ended in which it focused on Goku Jr. but I don't think Vegeta Jr. was shown. If there ever was some more movies made, they should be made to happen after the Buu saga. I'd love it if somehow Broly comes back & upon returning, he reaches an all new form never before seen or at least reaches the SSJ3 form. I'd love to see something to that extent in which everyone joins in the fight. That means Gohan, Adult Goten, Adult Trunks, Vegeta, Goku, Piccolo, etc. I'd love that. But, it probably won't happen. I have a better chance of buying the rights & making more movies myself.