The IE team have Today announced on their blog that IE7 (Seven) will be pushed out to Windows XP users using MS automatic update (contrary to what Chris Wilson told Vitamin). This will happen some time in the fourth quater of this year.
I believe this has huge implecations for anyone that develops commercial sites, you need to ensure that your sites won’t break in Seven, so start testing now.
Remember that a lot of CSS hacks that have been useful in IE6< will not work in seven, but the box model is still broken (in quirks mode)! Rather than using hacks, MS recommend using IE conditional comments.