If you ask residential consumers most of them will tell you that win 7 is running fine and they see no reason to upgrade to a new OS. Furthermore, most businesses will stick to win 7 due to its lower license fee compared to the new win 8.
That's what I've seen in the industry. Today's businesses won't pay the money to get a brand new OS on all their work stations. This is precisely why XP has lasted so long. Even here in a federal government building, a little less than half the work stations are still running XP.
If you ask residential customers they'll tell you they want to stick with XP and most business will too. Heck, most old school business will tell you 98 runs fine. So I don't see your point.
However, anyone that actually works on the computers and has to keep the running smoothly will say that the longer an OS is out the more painful it gets to keep it running smoothly. I support a huge number of XP workstations, and they stuck to maintain.
Win7 isn't going anywhere, people need to realize that just because Win8 is released, that doesn't mean everyone has to upgrade to Win8. However, we need a place to move forward. We can't just sit on our hands like we did with XP because it is "good enough". Win7 is a great OS, and I won't recommend any client to upgrade to it on an already existent machine. However, when they buy new machines they certainly will have Win8 on them, and that will be a good thing. We should never be in a position again where we go through multiple generations of workstations with the same OS. Every time you replace your workstation, the OS gets update at the same time.
I think it's mostly because vista fail hard with the driver side of things at the time of its release, also, it does ask for higher system requirement (real life, not ms recommended) than 7.
And imho, snap is the best thing ms did after xp sp2.
The driver issues were really the hardware manufacturer's fault. It was up to the hardware makers to make sure their hardware had drivers that worked with Vista, not Microsoft's. It was just like Windows 2000. The hardware makers dropped the ball with driver support, but the OS was actually pretty damn good, but got a bad name at first because hardware didn't support it.
And I don't think Vista has higher system requirements, at least I've never seen that. It uses ever so slightly more RAM and CPU power, but when it comes down to it if a machine can run Win7 smoothly it can run Vista smoothly. There isn't a machine out there that will chug on Vista, but magically run nice and smooth with Win7. And I think with the updates that Microsoft has done to Vista, the difference in resource footprint between Vista and Win7 has become virtually non-existent.