Even before HD-DVD and BluRay hit the market en-masse, next-generation, CD-sized holographic storage is underway - "Holographic Versatile Disc" or HVD stores 1 Terabyte of data on a single CD/DVD-sized disc.  That's a lot of movies on one disc :).  If it gets cheap enough, I imagine you'd be able to buy a movie, album, or game, then later "unlock" dozens of additional titles on the same disc to play at your leisure. (via Engadget)