I'd like to see a neighbourhood added that has both beach houses and some apartments. I don't like that Sulani is the only place where we have a few beach lots.
Maybe some sort of LA inspired world, with perhaps a pier with some amusement rides. Could come with some new boats as well that expansion, maybe some nice speedboats and the ability to water ski behind them.
Also becoming able to build some sand castles or sculptures, adding some other beach vacation stuff as well like volley ball. Possibly there could be like a hotel too at the beach where sims can go on vacation. Or could even own the hotel and run it.