The studio is likely focused on hammering out and polishing the modding tools, especially world builder due to its ease of use - anyone can use it regardless of prior programming or modelling experience. And greatly expanding and polishing the more advanced modding tools; SDK, Asset Editor, etc. in an attempt to greater support and kick-start the modding community.
They're also almost certainly focusing on bug fixing, rebalancing and polishing over the next few months. I think everything has been pointing towards Civilization VI breaking the mould and going towards a 3rd Expansion, so preparing the base for even more gameplay systems will be vital to making a 3rd Expansion work properly.
I think DLC will become harder to justify for the development team, with the release of a fully in-game based world builder I believe they will stay away from releasing map packs. Additional civilization packs are also unlikely, I think the 3rd expansion will round off the rest of the civilizations that will be in the game. Ed Beach himself has said it's getting harder to create uniquely distinct civilizations and it seems some of the UI has been designed with only a few more additional civilizations in mind.
I don't think we will see any additional DLC until after a 3rd Expansion and its subsequent updates, so around Q3/4 2020. Even then I highly doubt they will introduce new civilizations, maps or gameplay features, more likely they'll be scenario or wonder based.
I think there is in fact potential for smaller DLC packs after a third expansion.
For one, alternate leaders would be extremely easy to implement in packs of any size. It just depends on how many personalities they are still wanting to include (and I would say at the very least we can/should expect another six-ish, given how Germany, Arabia, Russia, Egypt, and China are designed, as well as the Rome/Byzantium problem).
For two, "semi-clone" civs (like a Spain civ renamed "Portugal" or a Scythia civ named "Huns") would also require absolutely no mechanical innovation or reconciling. It would just be giving players more content with primarily only aesthetic changes.
For two.five, "hybrid clone" civs (like a "Mughals/Gurkhani" combining Persian and Indian uniques or a "Byzantines" combining Roman and Russian uniques, or an "Austria" combining German and Hungarian uniques) would be similarly easy to implement. Just a thought.
For three, there is still some small design space for "alternative game modes" that could facilitate smaller DLC packs. Imagine a cooperative game mode with two civs with "group hug" abilities. Or a game mode that limits itself to a particular era, like the prehistoric era, with two civs with specifically hunter-gatherer abilities.
I'm not saying any of this is guaranteed to happen, but I do think that it would make sense both under Civ VI's design philosophy, as well as its marketing philosophy. Because ultimately what VI wants and what the players want are two different things. VI wants its roster and playstyles to be as diverse as possible. Players just want Portugal, Byzantium, Babylon, and Austria again, all of which would be mechanically and aesthetically quite boring compared to the design potential of Bulgaria, Swahili, Burma/Vietnam, Ireland, Italy/Vatican, Colombia/Taino, Hawaii, Inuit, etc. etc. etc. A model where the devs can release
great game design in the main expansion packs and
less innovative fanservice in the DLC packs seems to hit the happiest balance for everyone. Players still get quite a bit of what they think they want--they still get Portugal and Byzantium eventually--but they are also encouraged to live through the growing pains of accepting a broader idea of what makes a civ game good that includes things like Australia, Georgia, and Phoenicia.