MY COMMENTARY:
"Location, location, location": what happens to a given vacant storefront will largely be determined by *where* that storefront is.
Sure, there will be new ventures, for-profit universities, local health clinics, and other innovative uses of many of the cheap, vacant retail spaces that are located near population centers that can support those enterprises. And lower rents mean that new stores will be more spacious while older stores may be able to expand or upgrade more easily. But for many retail locations, the best solution will be to tear the building down.
Just think of the malls built in the Las Vegas exurbs to serve the anticipated populations of the massive housing developments that are now lying half-finished, deserted, and desolate. It will take years for the population to catch up with all of the speculative construction, and until it does, there will be little value to these empty storefronts.