Well most of the replies so far are well thought out and valid - so here's the opposite (MY reply - lol).

I think we've reached the point in this day and age (I'm talking mainly about Music here) where anything goes.

Any Genre.
Any Era.
Any type of entertainment.
From a 16 piece orchestra - if ya got's the money - to a 7 piece funk band, to a Jazz Trio, to a Duo, to a OMB all the way "down" to someone's Ipod and a big PA.

I don't think anything will REALLY replace anything else these days, audiences, the general public - hell, PEOPLE just want different things at different times and in different places.

That's what I love about living now - in the 40's we had Big Band, in the 50's Rock n Roll exploded, in the 60's Beat Groups, 70's got Heavy (disco in the latter part) 80's was downright horrible - I was THERE at least - 90's Grunge, and now the "naughties" 2000-? is one big fabulous melting pot with ALL these options available ALL the time.

Really, I think there's room for everyone these days - Ipods included.