I really don't think there are any real indicators that BluRay will ever overtake DVDs. The technology may skip over BluRay entirely.

Think about it... Music CDs have been made all but obsolete in favor of digital playlists which are downloaded. When a new album comes out, we no longer think in terms of purchasing a physical disc that we carry around. Why should movies be any different? 5 years from now, Blockbuster may completely abandon the rental of physical discs at storefronts in favor of sending out movies for download. They are already starting to head in that direction now. Apple is as well.

If BluRay doesn't become the dominant movie format of choice, why should it become the media disc of choice? I think it's more likely that the movie industry will follow the lead of the music industry, and the computer manufacturers will follow suit. After all, the CD-ROM didn't become the standard until after the CD was the standard for the music industry.

5 years from now the available bandwidth may be so great, you may very well be downloading OS 15 from the Apple website. MobileMe may give you 20 terabytes of storage space which you will use to hold your entire software collection which you download on demand. The MBA already has no CD drive. That could very well become the norm for all PCs.

(Maybe a little off the subject, but interesting to speculate on what direction things may take.)