As Greg mentioned the Sony A7s looks like a camera built for low light work, full frame 12 mp with large 8+ micron pixels. Low noise can be pushed to amazing iso of 409k
Maybe the big camera manufactures have seen the light and reverse the trend for increasing the mp on each new model.
This new cmos sensor also has larger lenses overlapping the grid structure between the pixels giving it higher than normal sensitivity.
Clear skies Ken.