While we're all speculating on the eve of Photokina announcements, it will be interesting to see how much of Panasonic's full frame camera is in a new SL, and vice versa. Very unlikely to be a direct rebrand like the lower end PanaLeicas, but it may share some internal circuitry or mechanisms like autofocus.
Interestingly, a metadata dump from an X Vario image revealed the word, 'Panasonic', and the X Vario is supposed to be a 'pure' Leica camera. So Leica has already been using some form of Panasonic technology in its own cameras, apart from the rebrands.
We shall see!