Django models only work insofar as all clients are interacting with the database through django. If even one other path to the database exists, the django models become unreliable as a source of truth. With the profliferation of microservices written in different languages, it would be nice to have a cross-language, shared-service solution as simple as django models. Something like protobufs or JSON might work well, but ultimately you still need to write a messaging and persistence layer for them, so it's not as simple as just writing a few model files.