Can be anything!
I really want EP10 to be about music and singers, bands, recording studios, live shows and music videos.... but I don't think it will happen this time. Maybe they will keep it for EP13 or 14!! But they should definitely bring our musicians sims back to life in TS4!!
Also hoping for: Romance and zodiac signs, Family gameplay and better babies! Another vacation world! Sims with PERSONALITIES!! Cars! Plain! Train! Hobbies! Farming! Circus! Teens and high schools! Models! More supernatural! Weddings! Zoo! Shopping malls! Classic items and worlds from past sims game! Time machine! survival! Funerals! Another creepy world! SOME gameplay for elders! Burglars, Bonehilda, and all the classic NPC's! Work places and cool careers! Haven and hell! Angels! Amusement park! CAW tool! Color wheel! Spiral staircase! And so much more! ?