Maybe for Skylines 2 … : )
You need before an upgrade of the agent limit, to manages more agents, more tiles and more cars so to manage a taller map. Also, you need better computers to manages such agents, so I think we are going to wait !
Because if you built a dense city with skyscrapers, agent limit can not manages more than 750k citizens, not more than 64k agents in the same time and not more than 16k vehicles (including metros, cars, trucks, planes, bicycles, …), which can easily be reached with only 25 tiles and good interconnections (Paris, in real life, measures only 25 tiles and is made of 2 500k citizens, 1 000k cars/hour, 5 000k agents. Imagine computing this when you are lagging with 16k cars !). Also, you road network will be limited to some length, which will surpassed if you built a low density city.