I loved 3, but I've held back for the moment because Paradox games take a year or two to mature and I'm playing other stuff currently. I know that the launch system pass covers 4 DLC lasting the first year.

I've watched a bit of it being played. The game is an evolution of 3 as you'd expect, and the graphics and sound are very polished. The city building looks better than either 3 or Planetfall from what I've seen. You expand your city centre into the regions around, adapt to what terrain/resources are nearby and set up adjacency bonuses a bit. A little bit like Civ 6 but simpler. You have separate production and queues for city buildings and units so there's a different kind of specialisation possible compared to before. I've heard a couple of people say bad things about the AI in its current state, but I didn't particularly pick up on anything being wrong in the little I watched. Some mods started to emerge as well. I'd say it seems like a very good prospect, especially with some more patches/content piled on top in future.