Bitcoin is known as to be the biggest cryptocurrency. in some countries it can be used to purchase goods and services and some see cryptocurrency as a threat.
if Bitcoin comes to be number one currency in the world today, can it be hijack by the government?
Hijack in other words steal? I don't think so. Unless government could access your hard earned private keys then nobody can ever access your cold wallets besides it is a crime. Furthermore, governments would probably be implementing regulations to cryptocurrencies and that would probably be worth something to them.
I really think that what the person that began this thread means is if governments can take control of bitcoin and even if it is unlikely the possibility of that happening is not zero, this is especially true because this market is based on freedom so governments are free to participate in it and try to perform all kind of strategies to take control of the network, they can make thousands of attempts but they have only to succeed once in order to get their goal.