I don't think there's ever going to be a threshold moment. I think we have to acknowledge at this point that many of the traditional methods you'd use to contain a pandemic (like contact tracing and isolated quarantines) just aren't going to work in the US. Places like NZ, Iceland, and to a lesser extent much of continental Europe can do this, but that moment has long since passed. There's nothing that we're realistically going to be able to do to get down to 1000 new cases a day in the US any time soon. Nothing. If we have 500k or 1,000,000 active cases, what are you supposed to do, quarantine the people they've come into contact with? That'd be like half the country. So to that end, I can get behind somewhat limited re-openings, simply because we're acknowledging failure, and making a surrender. The idea behind the spring shutdowns was buying time to study, develop testing, and prevent worst case scenarios. The best we can hope for is a combination of things: learn more about how it spreads, viable treatment methods that increase the survival rate, cheap, reliable and accurate testing readily available and make some adjustments for interactions (social distancing, mask wearing and the like). Obviously a vaccine considerably helps, but having a definitive "there is a vaccine!" moment where the world reverts back to February 28 is not realistic.