The absolute power add on is quite funky (got it in the steam sale), as it added some good buildings and the megolamania edicts.
I hope that Tropico 4 will add much more in the way of buildings, the only thing you can really see in the trailer is that they have big cruise boats... so maybe tourist docks can be expanded upon, host cruiseship tours or something?
Volcano eruptions sound quite cool, especially if they take more of a live action SimCity style disasters rather then a simple event notification (oh no earth quake happened! you lost 3 buildings and 5 people!).
Also, let us control the military in conflicts... the combat was the only horrible part of Tropico 3
