The part that is starting to worry me about bitcoin is the large mining farms, and how the regulators/lawmakers will start to interact with them: https://www.ccn.com/chinas-bitmain-gets-approval-for-us-bitcoin-mining-operation/
The fact that a mining operation needs approval from the local politicians should give every bitcoin investors some pause. It is for this reason that I believe POS cryptos, or cryptos that are CPU minable + POS, will gain more traction over the next few years.