if Bitcoin comes to be number one currency in the world today, can it be hijack by the government?
Governments cannot "hijack" bitcoins based on authority and regulation. They have standards to regulate people who don't use bitcoins, but "expropriation, confiscation" would never have been if they didn't want a worldwide riot to take place. Bitcoin is not a crime, people have their own freedom. I am sure they understand and seriously think about this aspect.