Here's my barroom analysis:
Theoretically there are two factors that make this virus dangerous:
1. Experience elsewhere in the world suggests the transmission rate is high under normal social conditions. Say 2:1 or 3:1. If those numbers are accurate, the infection will spread exponentially. Are they accurate? Dunno.
2. Experience elsewhere in the world suggests a high rate of infections require long stays in ICU, with some of those cases dying. What rate and how long and how many? Dunno.
But there is some combination of transmission rate and hospital load where the healthcare system gets absolutely gummed up. If that happens, they must deal with the scenario where large numbers of patients who normally would have been treated get triaged to to end of life instead. I assume that would mean all major cities start digging mass graves, because what else do you do with 1000s of unplanned dead bodies all at once?
The purpose of the lockdowns is to lower transmission rate below 1:1, where it will essentially fizzle out on its own as long as we remain locked down. Again I've read that experience elsewhere in the world suggests this can be effective. Again, I'm not aware of any especially convincing evidence of this.
Given this model, the optimistic outcome is a short lockdown will buy enough time to come up with less harmful interventions. For example, better testing would allow healthy people to return to normal life while keeping transmission rate below 1:1. Or improved treatment would reduce the load on the healthcare system. Or a vaccine. Or maybe the estimated parameters are too high, but we can't know until more testing is done.
Less optimistic outcome is lurching along in uncertainty while the economy implodes, followed by the unpopular mass grave scenario.