Well mono vinyl lasted perhaps 40 years (1920's to 1960's), stereo vinyl 30 years (1960's to 1990's, say), stereo CDs 20 years (late 80's - now), multi-channel audio CDs ? years. But isn't there a trend here (somewhat forced by me and ignoring reel-to-reel,8 track, and cassettes) ? It seems that the velocity of turnover of formats has accelerated as the manufacturers 'improve' their product cycles. Problem is that the consumer is getting confused. 'Cause now we have to decide Audio vs. Audio visual (home theater). I'd suggest there's more value-add to the consumer with adding visuals than adding additional channels. But with the home theater you get both, with somewhat reduced audio quality (remember home theater has had it's format problems what with VHS, Beta, Laser Disk, DVD).
But any way you look at it have moving parts in a player to pick up digital signals is dumb. DUMB. There will be a day when you either can download content or purchase it on a static memory card. Main problems will be identifying the content in your library, and fixing a format so we can 'invest' in audiophile players. The more things change the more they stay the same.
Oh well. I needed to rant about this 'cause I just went red book 'cause I would have to 'upgrade' my Pre-amp/processor to do multi-channel pass through, and it's only 3 months old. Why can't the manufactures of players do a digital signal so we can software upgrade our processors to use the new format ? B*st*rds !