I'd love to know what it is so I can plan my gameplay around the pack. E.g. if it will be bands or music I will keep aging off until it arrives, because I want Michelle Benali to quit her fitness career and start a career as a singer. If it is Generations I will start playing my single Sims more until the pack comes out so I can focus on the family game play again. For a romance pack it would be the other way around. If it is Werewolfes or Fairies I will continue my game just the way I like because these packs do not interest me at all. If it is a school pack I'd focus on my families with toddlers and very young kids or kids and very young teenagers depending on the packs exact theme (middle or high school). If we get a pack about France I will focus on my rich families (Goth, Alto, Landgraab, Lobo and so on) to plan their next trip abroad. Diana Landgraab nee Kruger could even have a relative (younger sister?) living there.
So EA, in conclusion please just let us know the next theme of your EP ASAP so I know which part of my Sims world I have to focus on. Pretty pretty please!