My guess is that firmware matters little, except white balance. If the camera gives a 'better' white balance the images will be 'better'. Unfortunately, what is better is in the eyes of the beholder. What I assume is that Adobe measures CGA response using a monochromator and calculates "profiles" from those data.
You can use any white balance in Lightroom/ACR, but if the camera produces a nice WB point it is most helpful.
If you build camera profiles using Adobe DNG Profile Editor or ColorChecker Passport the software ignores WB, but a good white balance helps when you apply that profile to an image.
firmware does not alter CFA characteristics and if Leica does not use (most probably not) what some people call "WB preconditioning" (or any other extreme ways to modify raw data postcapture) then your raws are still the same in terms of being worked with using raw converters... however new firmware affects most probably OOC JPGs generated in camera - hence your thoughts...