I don't think brick and mortar bike shops will go away completely. It's more the Independently owned LBS that's endangered.

I think what will happen, (and we were just talking about this in another recent thread) is that the independently owned shops will get swallowed up by big chains like Performance or the big bike companies and equipment distributors opening up their own storefronts.

That's just my very humble observation, of course, but that's been the pattern with most other specialty retail shops in just about every other category so I think it's a safe bet with bikes as well.