But unlike a VHS and cassette DVDs and CDs are the same size.
True, but it's all based on how the discs are made. Blu-rays, while the same size as DVDs, can hold up to 25 gigs (single-layer) or 50 gigs (dual-layer), so the "same size" argument can't really be made - the most a DVD could hold is 17 gigs, but only on rarely made double-sided, dual-layered discs.
You could fit everything DT has released (audio wise) onto a single-layer Blu-Ray and have room leftover!
Sure, the media format for video has always evolved and been a part of many format-wars (Betamax vs. VHS, and then in the hi-def era HD-DVDs vs. Blu-ray), but for audio it has always been a sort of smooth transition, from vinyl, to 8-track, to audio cassette, to CDs, which haven't changed much since their inception in the late 80's (the only change I could think of is going from 75 minutes to 80 minutes on maximum length).
-Marc.