I remember on the Sims 3 store, they had the 'Lucky Simolean Casino' and if you didn't want the whole lot, you could buy the slot machines and blackjack/poker tables!
I would love to see a Casino gamepack in the Sims 4. An Atlantic City or Vegas type world with different casinos and possibly hotels that your Sim could stay in. The hotel itself would have child friendly activities (such as an arcade where they could trade winning tickets for toys. A family pool, indoor playground, family themed restaurants, etc) The casinos for adult sims could have slots, roulette tables, poker tables, blackjack tables, and other popular casino games. To make it closer to real life, the more your sim spends at the casino, the higher their rewards status gets (for instance, they would be able to play in a 'vip' section- bronze, silver, gold, platinum, etc.) the more money they will win. Also, your sim would be able to order different drinks from the slots and tables. Suppose you don't want to go to a casino, you can also try your luck with lotto tickets and scratch offs!
tl;dr: Casino GP that would work great with GTW, upcoming restaurant pack, upcoming kid's stuff pack, spa day, and GT.
(very niche idea I know! I'm sorry if I offended anyone who's against any form of gambling)