Will "flattening the curve" result in an even worse epidemic down the road?

Best case scenario of all these response measures would be stretching out cases over time so that the healthcare system can manage the load. And, if a vaccine can be successfully developed in time, the outbreak may have only one peak. However, there may be a risk that after several months of the new reality, people get complacent, stop washing hands, start gathering in large groups again, etc.; and if the virus is still active, the virus might then infect everyone even worse in a second outbreak. I hope to see some discussion about such a possibility.