There won't be a proper second wave as authorities, companies and people are wary and hence will take precautions to prevent it. A lot of companies are allowing workers to work from home for the foreseeable future especially if they are vulnerable. And many people I know are still choosing to limit going out in crowds etc, all of this kind of behaviour will help prevent a second wave even if restrictions are relaxed further including the 2m rule.
I know on the whole the young don't suffer too badly from the virus but I would like to know at what age does it become dangerous for them, 40, 45...? The creation of a vaccine is still the best option for returning to normality especially as they suspect immunity is only about a year.