We don't even know if Blu-ray is gonna be the next format yet. Seems there may be a format war between Bu-ray and HD-DVD a la Beta vs VHS from back in the 80s.
But, my money is on Blu-ray....Sony is going about it very intelligently...they have a ton of movie studios commited to the format....and most of the computer industry. What's going to do it is PlayStation 3. That's coming out next May and it will have Blu-ray. Perfect way to introduce the format and get the ball rolling on it. HD-DVD lost before it ever even got out the door.