But no one "supposed" for DVDs to disappear. It's a prediction based on market forces, not a pronouncement by some dictator.
DVDs are still sold because people buy them. And they still buy them because they are cheaper than Blu Ray disks and there is a large installed base of DVD players and non-HD TVs.
In 5-10 years or so when most of the old non-HD TVs have died, then you can expect for pre-recorded DVDs to slowly become extinct. Eventually it will no longer make economic sense to manufacture them.
It's no different than pre-recorded VCR tapes being made long after DVDs became a main stream product.
When they switched from analog to digital last year - over 20 million vouchers to help pay for the converter box's were used. This means 20 million standard-def televisions are still in use and cannot use Blue-Ray.
Blue-Ray also incures a fee to Sony for every title produced so it's a lot more expensive to produce and sell and it lines Sony's pockets.
Hollywood actually hates the BluRay format because the production costs are higher and the number of duplicating studios that exist to handle the format is still not very large so the prices are high and the wait-list is long.