If Sony does make a A7x with a 50MP MF chip, then things will get very interesting very quickly. It's all the same chip in Pentax, Phase, Hasselblad and Credo. Sure there are some "tweaks", but the chip is the same. It's a great chip. It's long exposure at base iso surpasses the Nikon D800 and D810 from what I have seen. If Sony puts the chip in a RX1 body, then things will stay the same a while longer as that body will not allow for a removable lens. I wouldn't be surprised is Sony has a non compete clause with the MF companies for a period of time, just like they did with Nikon and the 36MP chip. Sony had to wait a year before they could but that chip in their mount in the A7r. Imagine what the A7r would have done to Nikon sales of D800's if both cameras were announced and shipped at the same time?
Now take the A7x with the 50MP chip, with a Modified E or new mount, put that camera on a Arca Universalis, or Cambo Aptus, add a 40mm HR-W and you have a very very good solution. Even if the Sony A7x with 50MP costs 5K to 7K, it will still be so much less than the MF companies. Sony knows EVF technology, and peaking, so both of these would add to the package just as it does with the A7r.
I have used the bigger Arca M2 in the DSLR2 configuration on the A7r with the 35SK, 40HR-W, 60SK, and 90HR, and it's very powerful combination. I hope to have a finished review of this up on my site soon. This same setup with a 50mp MF chip would be amazing.