It just becomes another reason for people to make the switch, and I doubt they will win them back when they finally do decide to upgrade to windows7.
But Microsoft has made it pretty clear that they do not thing you should be running XP. You're getting critical security updates only until 2014. And it's rather tricky to purchase a new copy of XP (you pay a premium and it typically involved buying a new OS first)
If you can't (or don't want to) upgrade past XP, but want modern browser capabilities, just use Firefox, Safari, or Chrome.
Although Mac support will probably come before Linux support, if ever. The Microsoft Office suite is available for Mac.
I just found out that IE used to have Mac support (http://en.wikipedia.org/wiki/Internet_Explorer_for_Mac).
Second of all, the fact that microsoft continues to decrease in market share while only releasing its browswer on one of the many operating systems available is no way to succeed. I know the linux community isn't large enough to draw much notice from microsoft, but is the coding that windows centric that it can only run on windows (no, since there will be a mac version... maybe).
I understand that not everyone enjoys this comment... Oh well.