I guess we might develop a vaccine in a few years. But we might not. And even if it's twice as effective as the flu vaccines, we'll still have millions of cases a year.
The consensus in the scientific community appears to be that we will have a vaccine in no more than a year. So, there is a outside limit on the whole thing. And nobody is saying shut everything down until there are zero cases of COVID-19 in the world. The point is to shut stuff down until we can flatten out the curve and make sure the curve remains flattened or goes down. We just aren't close to that at this point now and we can't make arbitrary decision regarding when that point will be until we have more information and evidence.