In the end, there will still be a profit, but those who bought at a price of 40k and above have regret, because they could buy now at a lower price. On the other hand, it is easy to do in theory, but it is more difficult to implement it in practice. No one could know at that moment how low the price would fall, or if it would fall at all. What if the price continued to rise and up to 100k?
This is always difficult, so now all that remains is to hold and, if possible, buy bitcoin now to average the price.
They "may" have regret or they could just realize that it's still an advantage because they bought bitcoin while some people still haven't. We need to realize that majority of the world's population do not own bitcoin, and these people may have bought higher but they do own bitcoin and that's great.
What they could do know would be buying a little bit more at a lower price and that way drop their purchasing price, that would allow them to make a profit earlier. On top of that they could just wait, I mean sure it would be better if they bought now, but they could wait and eventually they will profit, less profit than people who bought now, but still a profit is a profit and I doubt they would mind it.