According to Christopher Chapman, an analyst at Citigroup Inc, that might not be a bubble problem or fork which would eventually kill bitcoin, but the staggering energy costs associated with mining of the digital gold.

As Citigroup report states, the price of bitcoin required for mining to stay profitable in 2022 stands at $300 000 — according to the calculations, current growth trends, and electricity use. The amount of power consumed in the process of emission by that time would be enough for the whole Japan...https://en.bitnovosti.com/2017/11/10/analyst-in-4-years-btc-mining-wont-be-profitable-anymore/