I don't know the answer. I think ultimately, if distancing in restaurants is going to become the norm for any length of time, they will have to significantly raise prices to make the economics work.
Restaurants here are actually not doing too terrible because a lot of people are still picking up or taking deliveries. I ordered last night online, went to the restaurant and they dropped it in my passenger side window in the seat. Payment was done online. No direct contact. Those who adapt and provide workable alternative solutions should survive, at least in the short term.