The sale's being offered for a limited time only, so if you've been making plans to get one for yourself, now's the time. Especially since all these sales would seem to hint at a good ol' fashioned inventory exodus. Amazon's inevitably going to unveil a new line of Kindles in a few months, so it's going to need to clear out the last of the Kindle Fire HDs one way or another.
Of course, you could always wait and hope that they're going to go even lower, but with how cheap these things are now, if you're serious, might not want to risk it. More here.