There are several reasons why CD is king over things such as vinyl and cassette:
1. Convenience - small and can jump to tracks
2. Lossless quality - you can't get better sound unless you go from stereo to 5.1 or are at a recording in person
However, do you see CDs being around in 20 years. I don't. Sales of CDs have gone down to almost nothing as of late. Lossless digital is where it is at. I ripped all my music CDs and then sold them on Craigslist. Why keep them? Do people still use them on a regular basis? Not really. Mp3 players will make them obsolete in a decade.
Several reasons why I believe you are wrong
Blu-ray is not being adopted in high numbers because
1. Technology is still too expensive
2. Most people haven't experienced HD because they don't have a HD TV
Once you can get a blu-ray player for $30 at Wal-Mart and Blu-Ray discs for $10 a pop, kiss DVD goodbye. The other reasons is that HD TVs are too expensive. Once they come down in price, eveyone will want to watch movies in hi-def. People aren't used to hi-def TV yet. DVD also took a while to adopt, so will Blu-Ray. However, now that all TV is broadcast digitally, people will get used to watching all TV in HD. There will always be people who don't want to change, but those people are still watching VHS or no TV at all. I believe once the price is competitive with DVD and everyone has a 42 inch or greater TV screen, they will start picking up Blu-Ray. Now the price point might be as low as $10 each, but if it's low enough, people will want it. I bet the discs cost a few dollars each, so who knows what will happen.
Of course I could also see us completely jumping over Blu-Ray and going straight to digital copies of movies. With internet speeds increasing every year, what's to say we won't start buying movies online from Itunes. I can download a 10GB movie in a few hours. Once most people have FIOS or something equivalent, that time gets cut in half.
Now that I think about it, this is probably a more accurate prediction for the next 10 years.
Whatever happens, I'm excited about the new tech