It is true that businesses are upgrading to Windows 7 from XP, so there's no way they are going to do another upgrade right away to Windows 8, granted the pain would not be as great. But the cost would be scary enough.
As far as PC sales, Windows sales is tied to PC sales so the fact that has dropped is no surprise. Unfortunately, individuals and organizations are forced to upgrade Windows WITH new hardware purchases because new hardware has been needed to run the bloated Windows OS. If other operating systems were used, like GNU/Linux, the hardware upgrade prices would be much smaller. Unfortunately many would rather pay cash and stay on the same software, than try to migrate to something that has a lower TCO.