I doubt there will be a new Sim City. EA doesn't care about this game anymore. It's a very niche game, it doesn't have a very large audience, and in the end it's not worth the investment in its creation. The last three PC versions of the game, SimCity 4, SimCity Societies and SimCity 2013, each had just one expansion, and then the releases ceased. The reason is simple: the hype ends, the audience quickly decreases, and it ends up not meeting EA's criteria. Furthermore, Cities Skylines is a very strong game. EA doesn't care. :#
SimCity 4 had integration with The Sims 1, but it was minimal. And the integration with The Sims 2, for creating worlds, only existed because they took advantage of the SimCity 4 structure to facilitate the creation of maps. The Sims 5 Team is too busy to think about creating integrations with other games, especially one that isn't even in development. :#
The Sims 5 will be the The Sims we've always known, but with new features within its own universe. The big difference will be the optional online multiplayer, which will work as a cooperative, almost like Animal Crossing.