[avandonk]

Just my humble opinion. There will never be a better Canon camera for astrophotography. The 'new' Canon will be 22 mega pixels full frame. It won't be as good (signal to noise ratio) as the pixels are smaller. If you want to take terrestial pictures get the camera of your choice.
If you consider that a full frame cooled astro CCD (B&W) will cost in excess of 12K to 15K AUS, the Canon 5DH is a bargain. Let alone a good second hand one at a large discount!
By the way the Canon 5DH has about 50% quantum efficiency. If it was not for the Bayer filters on each pixel it would be about 70 to 80 %. The 'best' CCD's are the same. What is their quantum efficiency with a colour filter to take colour images, yes you guessed about 50% to 60%. Film has a quantum efficiency of about 2%!
Then there is the extreme cooling in the case of CCD's to lower the inherent noise. As you can see I am not a fan of CCD's ever since I realised that the only measure is signal to noise.
If my 5DH sensor had no filters and it was cooled to -40C it would make a CCD look sad. The A to D converter on the Canon is only 12 bits. So we may never know.
The CMOS sensors also don't suffer from 'blooming' unlike a CCD where charge 'leaks' into adjacent pixel and ruins a whole line!

Bert