I read it as the lifestyles come from the sims' activities and habits, so how you play your sim determines which lifestyle they get categorized into. So if it is acquired through gameplay I don't see why our existing sims couldn't work their way into a certain category starting at the moment we install the pack. I could be wrong, but that's what I thought they meant.
I'm just curious what they will be. My instinct is to think like Karon says, that it will be similar to favored hobby in Sims 2, but determined by what we have them do the most rather than randomly. Like a sim who upgrades appliances a lot will be a Tinker type, or something. That would be great for me, but people who give their sims more autonomy than I do will find a lot of their sims assigned to whatever lifestyle video games and trolling the forums falls under.
