To go up to $21k again maybe in the near future it will return to that price but with the current price still in the middle of $20k it means that there is a possibility that it will go down to $18k again and to reach $15k it won't be possible again in my range .
$21k isn't that far, we're at $20k so it will definitely be there again. With all of that said, every price that you can think of is very possible. From the lowest that you can think and from the highest that you ever imagine after it stays quite long @ $20k.
Everyone did not expect that the price of bitcoin drops fast and under $ 20k, even the lowest price is $ 17700, of course this makes newbie worried and scared, many panic and sell all bitcoin, but if we already know bitcoin for at least 3 years then we will understand That this is common, buying when a low price is a good start to achieve profit.
Every cycle, the market always has new investors and that's causing them to panic and it can't be stopped. But those who stay at these situations will be the ones that will be taking it all when we're all done with it and the bull turns back.