It is impossible to say with certainty which country will rule the world in the coming 20 years. However, there are a few countries that are well-positioned to become major powers in the 21st century.

• China: China is the world's second largest economy, and it is rapidly becoming a major military power. China is also investing heavily in technology, and it is becoming a leader in artificial intelligence and other cutting-edge fields.

• United States: The United States is still the world's most powerful country, but its influence is declining. The US is facing a number of challenges, including economic inequality, political polarization, and a declining military budget.
• India: India is the world's fastest growing economy, and it has a large and young population. India is also a nuclear power, and it is becoming a more assertive player on the world stage.
• Russia: Russia is a major military power, and it has a large and resource-rich economy. However, Russia is also facing a number of challenges, including economic sanctions, political instability, and a declining population.
• European Union: The European Union is the world's largest economy, but it is facing a number of challenges, including the rise of populism, the threat of terrorism, and the ongoing refugee crisis.

Ultimately, the country that rules the world in the coming 20 years will be the one that is able to adapt to the changing global landscape. The country that is able to embrace new technologies, develop a strong economy, and build a strong military will be the one that is most likely to succeed.

It is also important to note that the world is becoming increasingly interconnected, and no single country is likely to be able to rule the world in the traditional sense. In the future, we are likely to see a more multipolar world, with a number of different countries vying for influence.