Been reading about this in the past few days and even if I don't like it I understand why MS is doing this.
Windows 7 and 8 are both Windows Vista, if you consider the fact that Vista is 6.0, 7 is in fact 6.1 and 8 is 6.2.
Windows Vista was a huge step forward, even if many don't like to admit it but it had huge compatibility problems and it was a pig, in terms of system requirements.
However, Windows 8 comes 3 years after Windows 7 and 1 year and a half after Windows 7 SP1.
So it is somehow understandable that MS decided to add improvements and new features to Windows 8 instead of releasing a new SP for Windows 7.
To be hones, I was very intrigued by Windows 8 and MS's strategy. The first thing that came through mi mind when I heard that the Start buttons is gone for good and Metro is here to stay, was the selective install we had back in the Windows 95/98 days.
Linux distros have it, OS X has it and Windows had it. Why not use this. Make Metro mandatory on tablets and let the users chose on install if they need it or not. Install it if you must but give the users the possibility to enable/disable it as they see fit.
Then I realized that MS is falling behind on the mobile market and things started to make sense (for me at least and assuming I am not wrong here).
That's why I think MS took such an aggressive approach. They hope that after switching to Windows 8, seeing the similarities between Windows 8 and Windows Phone 8, users will chose WP8 over Android or iOS.
And now add this to the fact that you can have your Windows 8 Metro apps and settings on PC, tablet (RT or x86) and WP.
Now, if this is MS's strategy, a Windows XP scenario is to be avoided at all costs. Even if this means killing Windows 7.
Someone suggested that this will move users away from MS and Windows instead of pushing them to Windows 8.
I can't agree with this, especially when Vista didn't.
Sure, maybe some of us can do this. Start using Linux or OS X. But I doubt everyone (or a large number of users, so large that will determine MS to change it's strategy) will.
If you're a company that relies on Windows and other MS technologies, migrating the entire infrastructure from Windows to Linux or OS X will cost so much that will determine companies to stick with Windows 7 as long as they can and then switch to Windows 8/9 and invest in personnel training.
Of course, small companies might, but if a company is so small, they will probably won't be using MS technologies in the first place.
On the other hand, we have casual users that use a PC for multimedia and gaming.
If you're using Windows for gaming, chances that you'll switch to Linux and OS X are very small.
Also, I can tell you from my own experience that users using Windows for Internet/multimedia usually aren't too good with computers and don't like changes too much.
Those users will stick to Windows 7 as long as they can or they will try to find a way to get over Metro.
I find it more likely that they will try using Metro than switch to Linux (if you have problems with Windows, Linux will kill you for sure) or switch to Mac, if they have the money to do so. But if they don't see a reason to move to Windows 8 I don't see how they will see a reason to switch to OS X.
All these being said, I am thinking that, in the lack of a new SP, casual users will stop installing updates, thinking they will avoid weird problems that may occur because of periodically installed updates (not that most of them usually do) and they will start blaming MS because they have problems, like they always did.
Again, someone suggest that MS will eventually release a new SP, even if it will only contain all updates starting from SP1 till that day, without any performance improvements and/ore new features.
However, I don't recall MS ever doing this so I doubt they will be doing it now, when they try to move users to Windows 8.
That is why I find it more likely that MS will kill Windows 7 as soon as possible, pushing devs to Windows 8, than to face another Windows XP scenario and eventually a slow death on the mobile market.
In the end users will switch to Windows 8, one way or another.