The signs are not good for 8, that's a fact, and I personally think it's going to split the community down the middle. Thing is, people who buy a new PC (the general populous), won't know any different, and will likely just live with it (and maybe even like it), but a huge proportion (those who build there own kit and have to 'buy' their O/S, or corporates) will certainly avoid it like the plague. I'm pretty sure MS know this, which is why 8 is almost testing the waters for them. How will people react to the new interface? Will the reviews be any good? MS might almost have to give it away to get it onto desktops, but the deluge of Windows 8 tablets that will appear might be a different matter.
I can see 8 being relatively quickly followed by 9 (maybe <2 years) depending on how 8 is received, but I'm sure the MS marketing machine will go into overdrive when it 8 ships, no doubt saying it's the fastest selling O/S they've ever released blah.. blah.. blah.