Well, here's my take on it as a younger person in the crowd.
Audio as a hobby isn't going to die, but it isn't going to become big either. It will be what it is now, a marginal group. But it is going to change in the comming years. First off, digital will eventually be supreme. At the moment it is about as far along as analogue was in the 1910s, so it's still just a baby. But one day it will have grown up and will truly compete with the older analogue systems. With time it take their place. (If built well enough anyway.) Analogue will still hang around, but it will become a small part of the hi-fi world. Think about it, if you could get 100 bit 500khz+ HD downloads of any song in less than a second, would you put forth all the extra effort to get a TT to perform to the max? This is where convience will work it's way into the hobby. It's like useing the interstate and main highways to get to a destination, or backstreets and country roads. Both will get you there, but one is much faster.
Second, if you want to know the near future of audio look no further than your children. (For those here who have them.) Do they love hi-fi as much as you do? Will they pick up the torch? They are the inheritors of your gear apon your passing. If they do not love it enough to keep it up and going, it will be disposed of one way or another. It's the nature of things. I know i wouldn't be here if i hadn't gotten my father's equipment. This kind of "comming into" of audio may help get younger folks on board with the hobby, whether it be for the memories, or a true love of music.
Third, HD is moving into all aspects of life. Look at those commercials for "HD sunglasses". Well, i didn't know i needed sunglasses to see in hi def. So don't be surprised if someone starts marketing Hi Defination music and equipment. It may not be our standard of Hi-fi, but just like it did in home theater, it will start the trend towards it.
Forth, the way music is enjoyed is DEFINATELY going to be different. With what i've been seeing and reading about, i see two camps emerging. Those with gear of some kind, and those without. Those with gear will have all the wonderful stuff from today at their disposal, but others will be useing stuff unimagined today that can perform unlike anything before. Imagine your whole living room wall being a TV showing you the concert, while the other walls become the speakers. Kinda like a holodeck in Star Trek. Hell, you might even have holographic projectors to create an image of the musicians in your living room to go with the music! You won't be able to touch it, but it will look REAL. This kind of thing isn't far fetched, i've already seen experimental TV technology that is as thick as a placemat and just as flexible. It's a commin folks! The second camp won't have a need for gear, because they just download anything they want directly into their brains! Cerebral inplants with all kinds of different enhanceing abilities will be able to input any song of your likeing directly into your auditory centers. The ultimate listening expierence. This sort of stuff is also not far fetched at all. By the end of this century it will be as common as prostetic legs. Already we have linked quadriplegics to the internet. The rise of the cyborg is just around the corner.
So, those are some of my expectations for the future of the hobby, i could be WAY off though.