I'm not sure why Apple felt that
now was the time to commit to a new video interface standard. Actually, considering they committed before it was a standard, perhaps it was a move to tip the scales? On the other hand, so far Apple has only deployed DisplayPort on their laptops, the overwhelming majority of which will never in their entire life-spans ever be connected to an external display. (No that won't help any of the exceptions feel any better.) We'll probably see the same thing happen in a near-term update to the iMac, but not the Mac Pro.
Regardless, it's easy to see some
long-term advantages to DisplayPort. We're already bumping up against DVI’s limitations, and HDMI is shortsighted in so many ways.