You're forgetting the additional cameras in the standard and pro. These have turned out to be much more popular than I think DJI expected. There's a lot of room to improve there. Imagine a 1" sensor on each of the telephoto cameras on a Mavic 4 Pro.
And if you're looking at your
Mavic 3 Pro and saying, "it can't be done", you're clearly not an engineer
Or, suppose they got rid of the other 2 cameras and instead implemented optical zoom, covering the same range? I suspect there are a few people that would upgrade for that.
Or a new main sensor much lower noise with much more dynamic range. Can you say shadow details? Maybe a few still photographers might be interested?
There's a lot that can be improved with the camera without a larger main sensor. Add to that the Lidar and no-GPS navigation capabilities on RTH, and some other stuff DJI engineers are thinking that we can't imagine (spending most of your waking hours working on these things stimulates a lot of creative thinking), and I think a compelling next generation can be offered.
BTW, I love the leaked "baseball" design of the new gimbal!