Long answer: We don't want to constrain ourselves to a tightly set schedule as some add-ons take more time than others to produce, but we do want to keep them coming on a fairly regular basis. We've got several in the final stages of development as we speak; girl-girl, oral pack, new levels, a character tool, and some new characters, and we'll be releasing those as we finish them up. Besides those we have a lot of ideas for new stuff so there should be plenty to chose from in a relatively short amount of time.
With the character tool I mentioned above it will be free (no points needed) and allows people to easily create new outfits for the girls (and at some point the guys), and then they can share the outfits with other people (you can even sell them if you like), so we hope once people start using it that it will take off and soon there will be a ton of interesting clothing choices out there. The character tool will also give people the ability to easily create new characters based on the ones they have and distribute those as well. It should be exciting.
Short answer: we definitely have a lot of cool stuff in store and we'll get it out as soon as we can.