I believe the A7R has already opened up (high resolution) astro-imaging for under 60 sec exposures, at least it has for me (NM Album). The A7S can only improve upon this. The A7R gives me the same image quality at IS06400 as my Canon 60D at ISO1600. If the A7S pushes this to ISO25600, I'll be shooting 7.5 sec subs, or going deeper with 15-30 sec subs, or using a longer scope, whatever. If the A7S performance at ISO51200 is as good as the marketing hype, I'll be totally impressed .
Astro-imaging is the wild west at the moment; probably has been since the invention of the digital camera...
The images in your album are truly impressive, especially considering the stacked subs are 30 seconds or less, unguided, through a 65mm f/6.5 refractor using the high res Sony A7R. I can see now why you are champing at the bit to get your hands on the A7S! It could certainly be a game changer for near real time observing if the on the fly software applications that are springing up can eventually control the A7S and stack/process a handful of short subs while you watch the image 'develop' on the computer screen over a few minutes (or maybe a lot less) time.
Could you post one or two 30 second subs to show the typical amount of visible data and noise you experience with the A7R preprocessed - to get a feel for how much work the stacking/processing software would need to perform? Do you use any darks and flats? How much vignetting do you experience with the 65EDQ/A7R combo?