Worst case scenario: It is overtaken by govt cartels and it becomes another type of gold just a store of value with huge transaction fees, also it finds a stable price which does not augur well with "investors" and thus the perceived bitcoin bubble maybe a price of $3000 maybe not a pessimistic though 
if this happens then bitcoin will simply die. bitcoin exists and is strong because it is decentralized and it is a currency. otherwise a "store of value" or a "investment" is meaningless on their own and can not keep something like bitcoin alive.remember we are not talking about some closed source thing that nobody knows how to work. bitcoin is completely open source and the technology is out there. if bitcoin were to become centralized everyone would simply move to another decentralized new system.
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Best case scenario: Bitcoin lives to serve its purpose of being the internet currency with global adoption of-course "rekting" government and other central capitalistic entities. In a nutshell promoting financial inclusion worldwide.
i'd like to think the best case scenario doesn't involve "rekting" anything. bitcoin can still exist and be strong and even be worth $1 million+ and not replace or ... anything else. it can exist as an additional option for those who want the benefit of a decentralized currency, or for those countries with corrupted government.