It's really funny, but even though I have Tropico 3 since May, I haven't even started the campaign... The thing is, in city builders, I'm perfectly content to just build some free-build, sandbox cities, one after the other.
Maybe I'll yet see to that campaign before 4 comes out.

Isn't it a little early for a new game? What are they going to change gameplay wise to make me want it? Tropico is a great game, but I don't want and modernized clone of the last game with social features.

Not to mention the Mad TV remake.

We shall see what it's all about when it's out. They have highlighted a few of the more important features they're planning to implement, but I'm pretty certain that's not all, gameplay and game mechanic changes are probably not something about which they can tell us much about a year before release.