I can't see a uni series working, mainly because it wouldn't quite work with the premise of the show. The whole point is that they're Inbetweeners: they don't quite fit in with any of the social groups and are kind of the runt of the year. But at uni people don't have that problem as much. My mates and I were the equivalent "unpopular" group in the Inbetweeners mould, but we've all done pretty well at uni, seeing as there's as bigger selection of people and it isn't a social hierarchy. You can easily imagine Will finding a bunch of clever people, Jay finding a bunch of tw*ts, Simon finding some people who actually give him decent advice on sex. The series is so relatable because everyone has cringeworthy teen years, but most people only have good memories of uni so for them to carry on being social retarRAB would just be depressing.
Besides, uni's all about meeting new people rather than sticking with the same three.