Bitcoin is different from what we've seem before. If someone would try to compare it with tulips or dotcom bubble, than they would be straight up wrong - Bitcoin has value because it has many uses - storage of value, medium of exchange, international transactions, etc. The market might get overspeculative and overvalue those properties - people may be buying Bitcoin simply because they want to sell it later at higher price, so when the rally will slow down they will start massively selling and it will crash - but this doesn't mean that "the bubble will burst" and Bitcoin will get to zero - the process of price discovery will continue and a new price will be established. Then we might get another rally when people will see that Bitcoin has enough support.