In an article by Business Week magazine, Disney CEO Robert Iger is quoted saying that Blu-ray disc sales have not met studio expectations because many DVD owners are not replacing the DVD editions of their favorite Disney films.
Customers are not doing now what they did a decade ago when they upgraded their VHS libraries with the DVD versions of their favorite movies. “We have seen some but not as much as we would like,” Iger said.

Disney has tried in anyway to launch the Blu Ray recently, by releasing combo packs of their new releases including both Blu Ray and DVD versions of the films or by releasing the standard DVD version of one of their main 2009 title, Snow White and the Seven Dwarfs diamond edition, almost a month after the Blu Ray version.

Source: Business Week magazine