That's a very naïve assumption. Of course they won't add any of the stuff from expacks from the getgo. They need to milk it. I just hope pets and seasons come sooner. They will make it different in gameplay, though, you can count on that. TS2 added aging and wishes/fears, tS3 added moodlets, more developed personalities and an open world. From what I gather, personalities, emotions and interactions are going to be the focus this time. From that I assume the changes won't be as significant as those in 3, but still welcome.