Honestly, Parenthood is among the few packs that feel complete enough to me that I can't think of much to add in a refresh. Two and a half years ago I might have suggested a teaching career, but University has that covered. Of course, children riding bikes would be cool, but that's something that belongs in the base game, now that Cottage Living technically comes with a base game bike for adults.
If anything, I would like the teachable character values to be rebalanced, because as it is now, you get some of them (responsibility) almost automatically while others (conflict resolution) are out of reach for teenagers unless you make drama happen on purpose. Yet even that could probably be addressed in a patch, so I don't know. I'm looking forward to seeing what refresh ideas others may come up with.