When is a version a new version?
The key issue will be if and when IE 11 becomes available for Windows 7. Just as they did with IE 10 initially only being for Windows 8, Microsoft has again not done itself any favours in tying the browser to a particular version of the operating system. Until Windows 8 has reasonable takeup the stock MS browser on it will remain largely irrelevant to Google. They can even consider moving to not support Internet Explorer at all, which is largely what the extended support of Chrome for XP is about.
Technically, IE 9, 10 and 11 are all pretty close. Microsoft committed itself to a faster, more standards-compliant release strategy with IE 9. I'm sure the browser developers would themselves have loved to been able to backport the various versions to Windows XP but management scotched any such attempts.