I don't remember them announcing the other sequels this early, tbh. I'm sure we'll here more near Christmas time for another Spring/Summer release. Lets not forget, this is an EA title and it's been rolling through the annual release on the EA schedule so Skate 4 or some kind of major sequel is likely, especially if San Van Party Play DLC was the last DLC for S3. Sounds like they're moving into dev mode again.
Also, I agree about the sizing and design of spots. I think if I had to rank the 'maps', I'd say Skate 2 was my favorite. I loved finding the secret, grungy spots to skate and S3 doesn't have many. Most of the areas feel like a 10 lane highway, and that's just not fun to skate. I understand, they opened the game up to have the 'teams' skate around with space, but I'd rather it feel more real and organic like S1 and S2.