Perhaps the point I was trying to make wasn't clear.
Certain enterprise customers will always want to work with what they know, (i.e. typically Windows XP and Microsoft Office currently.) So this will be the long tail that Microsoft will coast along, if/when consumers migrate their personal computing to other platforms. Granted, there are certain situations when using an older technology such as mainframes makes complete sense, and there is little benefit to risk a major system upgrade; but there are many other situations where not upgrading seems lunacy (e.g. in an era when people want to have much of their banking online, the old mainframes in the background struggle to cope with the demand.)
As an aside, I interned at a bank where one of the tasks I did was adding HTML tags to predefined paragraphs that were in plain English. I did this in Excel, manually, line by line, on a PC sporting Windows XP and a 15" monitor. This could have been done in seconds with a shell script if anyone there had a clue. This kind of ignorance is a godsend to Microsoft who will continue to sell software licences to clueless companies for the foreseeable future.