DisplayPort has much higher bandwidth than DVI or HDMI (over four times single-link DVI and 1.7 times HDMI). DVI already can only drive a 30 inch display with a dual-link connection. DisplayPort doesn't have that problem. I imagine now that there's been a big push to get mobile screens up toward 300ppi resolution, there will be a push to do the same on laptop and desktop displays. Eventually, you'll need the bandwidth to deal with the extra pixels on large screens.
Pushing for higher bandwidth connectors is a good thing. Otherwise, we'll trade VGA for DVI as the obsolete technology that won't ever die.
"Experience has proved that some people indeed know everything." -- Russell Baker