Bitcoin has walked on thin ice for a long time already.
Bitcoin is a payment network with 5 million users and annual costs with around 5 billion $ just for the electricity and hardware (leaving out indirect service costs). That makes annual cost around 1000$ per bitcoin user a year. These costs are mostly paid by debt and high hopes of future value. When hope of irrational gains will start to crack, then the faith of debtors will start to crumble together with holders hope of bitcoins high future value. This will eventually create an avalanche that the world of finance hasn't seen yet. It's not a matter of "if", but "when".