People were making some amazing and awesome lists, but Ill keep mine simple. I would be happy with....
1. Bands/Singing career (Seattle type world to go with bands)
2. Horses ( also I miss the small birds and animals from sims 2 and 3)
3. Fairies
4. more occults
5. Some sort of future themed expansion like we had in Sims 3 would be fun, but thats not necessary for me.
6. I don't care about cars we can drive, but I loved the fixer upper car we had in sims 2 and then sims 3 from the store. That with a mechanic type skill would be so fun
7. More art skills for sims, we had jewelry making in Sims 3 and pottery in sims 2, that would be so fun.
8. Better teens that looks like teens (although I doubt this will ever happen)
9. Archery
10. Online dating and attraction system for adults.
I love the other stuff people suggested. The stuff below is stuff that would be amazing, but if we don't get it its ok.
1. More worlds such as another latin american world. I love Selvedorada, but I want one where its got city parts and the beaches. Im part Venezuelan and it would be beautiful to see a world with gorgeous tropical beaches, but also city life. I love Sulani and Selvedorada.
2. Would adore an African world.
3. I miss the World Adventures pack from Sims 3, it would be so cool if we could get that. Kind of like what we got with Jungle Adventures, but with more world options to visit and you have a travel visa just like in sims 3.
4. I miss the acrobat and magician careers from sims 3, those were so fun.
5. I saw someone mention dragons and yes, dragons would be so cool!!
6. Casinos
7. more stuff for elders
8. Bring astrology back
9. A cool space world kind of like when we got Lunar Lakes in sims 3.