Hoarders or hodlers who at first were greedy and euphoric will see their precious plummet in price and start selling en masse. It happened so many times that you could say it is a law of nature in the bitcoin economy.
Unfortunately bitcoin is concentrated in just a few hands... So the panic sell only does worse
Define a few though? There's been a lot studies and research done on the top 47 holders of Bitcoin. After guessing than Satoshi owns ~1MM (which who really knows), the next 46 drop off fairly significantly. Yes, I agree if most of then panic dump the market would crash. But I think we have enough of a support base right now to recover fairly quickly.