For me this is a sad post as you will read below.
I echo much of what K-H has recently written. However I am not into Nikon as I have a 5D3 for auto sports work and other fast moving AF work.
I will try the a7r due to its 36MP and like many here want to see which WA RF lenses work. I know what a high MP count can do for DR as I often use an old Hasselblad SWC with a newish P45+ digital back for landscape capture and is all I can say is WOW. It often gives me that old Kodachrome look to digital images where you can almost see the different emulsions on the surface of the print like you could see while "emulsion peeping" with a Kodachrome slide.
More importantly, I will also try the a7r for use with my many R lenses due to the fact that I do not find it tenable to have to switch off my M's while using EVF since it will lockup from over heating if I left on. That's way beyond beta testing as beta testing should come after this serious defect is remedied. It just does not work for me.
Who ever gave approval to final release of this camera, in its current state, should be fired. Since Blackstone's involvement in Leica two products have tarnished the Leica name in my mind-the M240 and the APO50, both of which I own in multiple copies. Perhaps they will correct both products to the satisfaction of most, but Leica it is too little too late. What have they been doing for 3 years while time marches on and competition leap frogs them big time?
Also, even with wide RF lenses I often use the EVF and the same over heating issue arises plus for street if the camera is shut off then the startup time causes me to miss way too many "in the moment" shots for an M model which has its roots with street and journalistic work.
Since I use EVF with R lenses routinely, I say why not see if another (way less expensive) camera with even higher MP performs better than my M's.
While waiting way too long for my first M to arrive I got the RX-1. My first non-Leica for street. Someone on this site helped with the initial setup, which I configured once and have never felt the need to change it again. What a revelation for me to the detriment of Leica.
Thus, already seeing the benefit of AF in a small RX-1 body which never overheats while leaving the EVF on it and having it continually powered up, I can see very little downside in trying out the a7r for my needs. In addition, the a7r continues with the ultra-sonic help for sensor cleaning which Sony incorporated in the small RX-1, all while Leica said they could not do it due the small size of the M240. What a revelation for me to the detriment of Leica.
For me it is sad to see what Leica makes us deal with and I never thought I would think that. My M9P has finally come back from Leica NJ this week under its last warranty visit with a new skin and many interior changes they deemed necessary. I feel that I have moved past my beloved M9P and since I have a beautiful CCD sensor in my P45+, I now feel no need to keep it any longer.
If in the end I migrate to Sony I will keep my Monochrom as I love B&W which harkens back to the days when I began serious photography, nearly 50 years ago. Times have changed over the years, but it still is the photographer who should control the situation and with every modern camera I have found a way to configure them for that to be the case with my 5D3, SWC+P45+, RX-1, M9P and Monochrom, but sadly the M240 takes me a step backward with its current drawbacks where the camera is now too often controlling the situation and not me.