A few more bits of info:
Windenburg is as large as the Worlds of WillowCreek and Oasis Springs.
If you own GTW then you can own and run a cafe with the new expresso machine which makes drinks that effects sims moods.
Your sim can be in up to 3 different clubs but only one will be active at a time.
*edited: Just some thoughts on how this new club interaction seems to work. It seems that clubs can rival each other opening all sorts of possibilities up. As you are able to choose the activities you could have your sims do anything from playing video games to cooking to making scientific serums I guess. One of the gurus talked about a club that had two activities that they did; chess and woohoo. (We knew that would happen, right. Still it's the possibilities to make what you want that sounds fun.) Maybe as other game play features are added in the future, like maybe supernatural, you could have a vampire club where your sims go around causing havoc! It seems like the club system is really going to add a lot of game play to The Sims 4. More then the initial intro video let on!
Yes, someone on simsvip suggested that if we get witches, we could have wizard clubs. Slytherin vs. Gryffindor perhaps? The social groups in TS2 and 3 never appealed to me that much, but the clubs might be intriguing. Something I thought of -- with locking doors, our children could have clubhouses.
Also, someone on the official forum pointed out the resemblance between Romeo Monty and Juliet Capp and the couple in the trailer (the DJ and the red-haired girl). Don't know how intense the rivalry will get.