Now we have Sandboxie, supporting the NT-family, from v5.0 through the 32-bit versions v6, or Vista. For the first time in the history of Windows computing, users of these systems can determine when they want to (not when they have to) upgrade, whether to another Microsoft OS, or maybe to an entirely different distribution.
Assuming past experience with Sandboxie holds, if anyone is still using one of the supported NT-OSs when Microsoft "pulls the plug" on extended support, I can't see that anything will change overnight -- as long as one can continue to run Sandboxie.
I doubt that many (even Vista's early-adopters) will be running the same OS three years in the future (likely by then it will be Vienna/Windows 7, or ??) but it's nice to know that the change will now be at the user's option, and not as an emergency procedure because the current OS is about to be taken over by on-line exploits.