They are quick to take advantage of new Win8 features, and it took a while before their backport of some of them (Platform Update) to Win7 can be finally released.
That may make some sense if they were already ahead of the others with IE10, but they are about 2 years behind in HTML5 support. Spending another 6 months just to port it to a pretty similar OS of their own doesn't make me very optimistic about IE's future.
