I don't see mom and pop shops being compleately erradicated.. to be honest I see the exact opposite.. it's already starting to shift. As long as Aquariasts Demand the exotic, demand a knowledgeable staff, demand a wide variety of equipment,food, livestock for their tanks. Big business like walmart,petco, and petsmart will ultimately fail. Very rarely will you find someone in the hobby who walks into one of these stores after being in the hobby 1yr+ will go "Oh cool! Look at those Guppies!" Those stores cater to the "newbies" the in and out people.. They drop a few bucks, they take it for a test drive. They either
A.) want bigger and better things then they can get from their local chain and get frustrated and start finding other petshosp to go to.
B.) Say to heck with this! and an MFKer gets an awesome deal on a barely used set-up.
C.) return to these stores to get supplies, ect, kinda fade in and out. find a fish here 'n there to add. spruce up the tank w/ a new decor. and generally can go into A or B.. Time tells with these people.
As far as younger genrations getting into the fish hobby.. I actually know more peopel younger then I am (27) that are getting into fishkeeping then people in the 25-35 age bracket. Aquariums are deffinately making a come-back in colleges. "Micro-tanks" and particularly people like Amano, have opened a door to some people to look at aquariums in a new scope. Live planted systems are getting easier and easier for the average Joe. More is becomeing knowing about many rare and unique species. CB efforts of fish like the Zebra Pleco are showing people Aquariums aren't just fish coffins. Zoos and Aquariums are makeing better progress towards giveing their charges a more natural healthy environment in in turn the fish are perking up, being active, showing peopel what they really can be. Not just some "thing" in a tank.