It's inevitable that when moving from one game to the sequel, DLC features get lost. The Sims are absolutely among the worst of it, hence me not buying into new ones, but I'm not too worried about CK3.
Sure, it's to be expected that some features we take for granted now may reappear as DLC, but the material we have now implies that we'll be getting a lot of CK in the base game. Moar features in future DLCs, inevitable. Some might be old features we paid for in CK2? Maybe, but will most likely be built with new CK3 considerations in mind. So a far cry from having to rebuy the Pets expansion, Seasons expansion, University expansion each and every game forever.