I think versions of IE that only works with XP is the reason because it's really NOT A STAND ALONE browser like Firefox, Opera, etc. which is why older versions of IE will not work with Windows 7. As you know, MS always try to make all their software to have the ability to interact with their other software. In a way, that is a good thing except when you can't afford to upgrade.
I am betting that there will be patch that will allow the users to install them manually. Otherwise, XP is over 13 years old and if users just cannot upgrade then they should download an alternative software like Firefox.
From a web developer perspective, I look forward to XP being history even though it has been a very good operating system.