Will Windows ever be rewritten from scratch?

Bowler4Ever and Billy are both technically correct, though they stated different points.

Bowler4Ever seems to be stating his conclusion, but not how he came to that conclusion. I gather that he's arguing from a stylistic point of view; No matter how much work people put into anything, someone will always find a way of changing it. Whether or not that's an improvement can be subjective... Some people might like the changes, others might dislike the changes. That's why different OSes exist to begin with.

Billy suggested that an OS improves as it matures, as patches are applied. This was equally true in the case of Vista; The original release was garbage, and installing the service pack improved it significantly. Reinventing the wheel just doesn't seem to make any sense, as there will always be debugging and fixing of bugs. Throwing all of that progress down the drain would be silly.

However, when considering new hardware features such as VT virtualisation, future OSes would need to be modified so significantly to make use of that feature in particular that it would probably be unfeasible. All of that modifying of code, testing, more modifying, more testing... It is far better to write a new software product with a feature in mind than to hack the feature into old software.

Which features would this "virtualisation" concept introduce? Well, as it is, no matter which OS you use, all of your applications can see each other. They can all see the keystrokes you send, and some OSes even allow them to send keystrokes, move the mouse, etc; This is the reason keyloggers exist. Virtualisation would cause the program to believe it is the only program running in the system. Thus, when you send a keystroke to an application, no other application would see it.

To this day, there is only one OS that comes close to utilising VT that I know of: FreeBSD's jails are a form of software virtualisation. Who knows where that might end up ;)

No operating system will ever be perfect, no matter how much work and code goes into it.

For an operating system to better, it has to be upgraded or improved from the previous versions. Starting all over again may or may not yield good results(Vista LOL).

Of course, it's just my own opinion.