The upcoming Panasonic LUMIX S1R II camera (L-mount) will not use the same sensor as the Leica SL3. The SL3 has a new 60MP sensor. The current Panasonic Lumix S1R has a 47MP sensor.
The Panasonic LUMIX S1R II official announcement is expected on or around February 25th before the start of the 2025 CP+ show in Japan.
Recently Panasonic registered several new cameras online:
What to expect at the 2025 CP+ show? (an updated list of upcoming/rumored cameras and lenses)
Via camerainsider