Bitcoin futures are set to begin trading Sunday at the CBOE and a week later at the CME, and retail brokerages are bracing.

Interactive Brokers' founder Tom Peterffy said on CNBC's "Fast Money" on Thursday, his concern is that the cryptocurrency could continue to rise to $100,000 or more before crashing to zero, and could pull down small brokerages in the process.

Bitcoin's price has skyrocketed just this week from $12,000 to $19,000 and back down below $16,000. Futures trading is only seen as further legitimizing bitcoin even as some prominent market participants say a dangerous bubble is forming.