I've been wondering the same thing.
For years, people have been repeating ad nauseam that the worlds could not be changed. Then the worlds were all changed. Hopefully, that means that beach areas could eventually become more functional.
It was possible over a decade ago. I'm just not sure what is the particular hold up with the TS4 engine (especially, since functional beaches were bound to be highly requested). After the release of Seasons, seeing the beautiful beaches at Windenburg and Brindleton Bay, and still not being able to use them, it feels like we're being punked.
If the Gurus could be more forthcoming, it would help a lot.