I don't think Europe is ready to let nature takes its course.So at some point, without a vaccine, we will have no alternative but to remove the measures keeping the infection rate linear and let it explode exponentially. As I say check-mate. How can you plan for that?
a treatment will probably be found before a vaccine. That will shorten the length of stay in hospitals and reduce the workload for the NHS. Also, it will give some re-assurance to those under curfew.
As I said, we need to keep the lockdown pretty rigid until then.
As a guess, 4-6 months for a workable treatment, 18 months for a vaccine.