An AF adapter was announced for Leica M lenses on Sony A7XX. The adapter moves the distance between the camera body and the whole lens.
This adapter can be used with any lenses as long as the lens can be adapted to M mount, which is rather easy since most lenses has longer flange distance than Leica M.
It would be particularly for MF super tele such as Nikon EDIF 600mm.
However, a recent comment from a friend about the reliability concerns with mismatched voltage/current of lenses/camera scares me away, even if the adapter uses the same voltage as the camera.
The concern is it takes a huge power to push or pull the lens from the camera body, especially if the adapter respond quick. Yes, it can be done with holding the lens so that it is actually push and pull the camera instead of the lens, but most people have the habit to hold the camera body tight against the fase or the forehead, so it will become push and pull the whole person, the implact would be horrible.
The AF adpter uses the same priciple as of the Contax/Yashica AT camera body, but it was less a problem in Contax since in that it is moving the film assembly in the camera body.