I doubt that all of the big chains would go out of business at once, so some will founder. Apparently malls are a passing phase. I'll miss them when and if they totally disappear, but we should be able to get on without them. People are adaptable, inventive and persistent. I'm sure that as long as the economy doesn't totally fail, we'll have the stores we need.
If the economy does fail, well, we did get through the Great Depression. I'm sure that we find a way to get by.