I definitely think the base game update may mean more pronoun updates and body hair which was previously promised.
I think high school would be interesting but only if it's not super focused on the academics and more on high school experiences...things like acne, voice changes, proms, sneaking out, learning to drive, prom, first dates and first love, high school graduation, finding what you want to do for your life (hobbies, interests, etc), style/expressing yourself, private school, after school programs, etc.
I think they could incorporate a lot of things and fit the teenager theme.