Endless had districts before Civ did. Not 'themed', just one type basically. From what I recall you could either expand your city with a district or 'level up' a district.
However, I believe in Endless you only 'worked' the tiles directly adjacent to your city. So expanding with a district allowed you to work more tiles (at the cost of losing one).
Not sure if they'll do Humankind in the same way or not.
Given the pictures of sprawling cities in Humankind that have been released so far, I think a couple of conclusions are already justified:
1. You can build different types of Districts, given that some 'tiles' of the cities show different buildings/constructions in them
2. You can build the same District multiple times in the same city, given that identical street/structure patterns show up in multiple Districts.
I don't think they have released anything about the exact types of Districts, but given the pattern (inherited from EL) of Food, Production, Gold (EL's "Dust"), Science and some sort of Cultural/Political "Influence" being the basic denominations in the game, I'd bet on, as a minimum, Districts that produce each: Food/Farming, Production/Manufacturing, Gold/Finance/(Trade?), Science, and Culture/Influence.
After that, anything goes, but some sort of Harbor, Airport/Transportation Hub, and maybe "Wonder" District would be logical - the illustrations so far have shown District-sized structures identifiable as St Basil's Cathedral and possibly Etemenaki/Great Ziggurat, either of which could be a 'National' or 'World' Wonder. (And No, we don't know if Natonal Wonders are included in
Humankind - yet)
As always, the Devil Is In The Details of how Output is modeled from a given District, what modifies Output, how easy the modifications/bonuses are to get, are they modified by a Bonus from the Faction you are playing, etc.
I confess one of the Big Questions for me is Can You Change A District? That is, if a District is now excess to your requirements, can you 'demolish' it and replace it with another? Is Urban Renewal part of the game, as it is sadly lacking in Civ VI.