As far as physical media goes DVD is not going anywhere and will remain the dominant disc format. Blu-Ray is still overpriced, and your average viewer does not believe their is an appriable difference between their upscaled DVD and Blu-ray to make the leap (unbelievable I know).
The same argument was used against the Audio CD in the 80s (CDs beeing overpriced and the average listener wont appreciate the difference between Vinyl and CD) and it still happened in the end once the CD players became cheap enough. Probably also because the manufacturers/labels just didnt want to care about different media formats. Which makes me wonder if movie/tv distributors just one day just dont want to feature two formats anymore and just go with Bluray, so no extra costs for producing DVDs is needed (DVDs have a different menu and file format).