I think it will need a theme that might only be touching generations. We already got Parenthood, which in my book had lots of features that would have been perfect for a Generations pack. The only two things I miss are walking canes for elders, and baby/toddler strollers. In TS2 Generations was one of those packs I could not really tell why I liked, because there were no big features, but the gold was how it made hidden changes to how I experienced the game. Parenthood also did some of that whit phases and values/traits and more focus on school.
I can't really suggest a good theme for a TS4 Generations, except I'd like to see some focus on family dynasties, including testaments, heirlooms, genealogy, multiple homes and perhaps clan missions to make it more interesting playing two rivalling dynasties. I don't think going with kids to boarding/high school will be included, because it would be too much University over again.
Adding: Perhaps Generations could blend in with Farm Life? They would make for a good match, I think :)
