Don't know about DVD itself. But know of high definition Digital VHS (seen quite a few films released now) and the forthcoming Blu-Ray discs developed by Sony which may be a possible replacement for dvd, also supported by the likes of pioneer,panasonic,phillips.
I know blu-ray holds 27gb on a single layer and possible 54gb on dual layer with data rates of up to 36Mbps!!!! hold around 2-3 hours of high definition material...works using a shorter laser compared to dvd.