I think this is a very good question that every retailer wants to answer first. My opinion is that we'll see smaller specialty stores (such as Best Buy's "mobile only" stores) intertwined with larger necessity stores (such as groceries). Certainly, most items a person needs can be purchased online. There will probably always be business-to-business type stores, such as auto parts, equipment sales, advertising, etc. Retail is going to be an interesting ride though.
Perhaps we'll see them all give up and just invest in huge super-efficient warehouses and freight services. Imagine the big companies offering their own freight services to have absolute control over costs, and use it as a revenue stream for smaller affiliates. Certainly though the innovators are going to win, and the stagnates will die off.