This sort of catastrophic thinking has a paralyzing effect on people and does nothing to actually solve problems. You can't have a definite solution to a problem that doesn't even exist yet. Technology is and has always been an iterative process over time. Developments in quantum computing and encryption will likely be made in tandum over many years. We already see that happening with encryption standards now and have with classical computing for decades. Hence the reason we don't use certain encryption schemes anymore. This isn't a new movie.