Is there a new world and new premades with seasons?

There isn't any world, but there are changes to the public spaces in the old worlds.

The households from the trailers are available on the gallery (MaxisCreator_01)

I think the consensus was that they spent a lot of time updating the look of the existing worlds through each of the seasons (and heck they did an awesome job!) and therefore they didn't use that time creating a new world. I'm sure new worlds will come to the game in future. There is literally SO much else in this pack as well.
As far as Sims go, I know The Climate Family are on the gallery at least...