I am guessing a few things are happening. Panasonic is trying to get rid of the old 25MP FF sensor inventry. Which is why the S9. It's a good camera for the price and sensor size, but it has some issues which Panasonic doesn't want in the next generation of FF sensor.
Panasonic needs a New Sensor greater than 24MP and Way Less than 60MP (somewhere around 40MP if it wants 8k). That sensor would make it to most of Panasonic's FF Lineup. It has to be excellent for Video, and have Reasonably High Resolution for Photo. Rolling shutter shouldn't be too bad, and it needs a huge variety of frame rates and resolutions for video. My guess is, after Nikon's working with Sony, Panasonic too is trying to ensure it gets a custom sensor, with design and features almost exclusive to Panasonic. Also, it probably doesn’t want to have the exact same or similar models at Leica, so that the market is better spread out between the two.