"Japanese entertainment software developer Pony/Canon will release the first movie title on a hybrid Blu-ray/DVD disc in Japan in February, in an effort to accelerate the transition from the DVD to the Blu-ray format." Read the full article.
Sounds pretty interesting one disc that both DVD and Blu-ray players can read, so I guess you could have the standard definition version of a movie and the high definition version on the same disc! Might be handy if you don't have Blu-ray players in everyroom and want to watch a movie say on a DVD player in the bedroom maybe. Or you might only want to rip the SD version to your hard disk to save space. I can see having both SD and HD versions on one disc coming in handy, whilst we are in this in-between stage, until everything has switched over to the blu-ray format this might ease the transition.