At least one more expansion pack has been confirmed to be in development by EA. At the University of Florida EA revealed a few new titles last week while talking to the Students, including two (nameless) Sims 2 expansion packs. Assuming University is one of them, that means one more expansion is already in development now. If University isn't then we can expect at least two more EPs already being developed by Maxis, even though the first one isn't released yet. Maxis has previously already stated that expansions will come out at about a 6-month basis, so we should know about them within a year. Check out IGN's article for some more details.