The UN's Revision of World Urbanization Prospects has released their 2018 report. The findings have determined that another 2.5 billion people will be living in cities by the year 2050. The majority of the growth will be concentrated into the countries of China, India, and Nigeria. 

The report notes that China will see an expected increase in urban population totals of over 250 million, India 400 million, and Nigeria will have an increase of nearly 200 million. New Delhi is projected to be the city with the greatest population by 2028, surpassing Tokyo, currently at a population of over 37 million. While there is expected population growth in Africa and Asia, some cities in Central Europe and East Asia are expected to have a population decline. Specifically noted in the report were the nations of Poland, Romania, the Russian Federation, and Ukraine, all of which have had population declines since the beginning of the 21st century. 

Rural populations, which have been increasing steadily since 1950, are expected to rise slightly from their current totals of 3.4 billion, but reduce down to 3.1 billion by 2050. The UN Department of Economic and Social Affairs (DESA) notes that there will be specific challenges associated with the increase in megacities, defined as a metropolis with over 10 million people. 

DESA noted:

"As the world continues to urbanize, sustainable development depends increasingly on the successful management of urban growth, especially in low-income and lower-middle-income countries where the pace of urbanization is projected to be the fastest. [...]Many countries will face challenges in meeting the needs of their growing urban populations, including for housing, transportation, energy systems and other infrastructure, as well as for employment and basic services such as education and health care."