According to 1UP, reporting on a The Sims 3 reveal in the upcoming issue of Games for Windows: The Official Magazine, The third iteration in The Sims franchise will feature a much larger sandbox world, with events taking place in a wide-open, constantly changing neighbourhood.
With the host of add-ons for The Sims 2 players did get to pursue a range of activities, but each was more of a sub game rather than something integrated into the experience. The Sims 3 will change this, with what you do outside your home being just as important as what goes on within the four walls.
1UP also notes that there is a major change in how Sims' motives are handheld, with individual meters being replaced by moods. The hope is to remove the requirement to fulfil the daily eat-sleep-excrete routine, giving players more time to enjoy all the fun stuff going down in the town.
The game will also sport a completely revamped character creation system, more info on which will be found in the April/May issue of Games for Windows: The Official Magazine. Expect lots more on The Sims 3 soon.