Size of cities matters in terms of urbanization

Globally, more people live in urban areas than in rural areas, with 54 per cent of the world's population residing in urban areas in 2014. By 2050, 66 per cent of the world's population is projected to be urban. The world will need to shift to a focus on the degree of urbanization.

There will be the same rural definition.
There is small towns and suburbs. There is no unified definition small towns where some countries say it is 2500 people or more and other 20,000 people or more.
There there will be city dwellers, but there should be splits of the size of cities.
20,000 to 500,000
500,000 to 10 million
10 million and larger.

There is great diversity in the characteristics of the world's urban environs: close to half of urban dwellers reside in relatively small settlements of less than 500,000 inhabitants, while nearly one in eight live in the 28 mega-cities of 10 million inhabitants or more. The number of mega-cities has nearly tripled since 1990; and by 2030, 41 urban agglomerations are projected to house at least 10 million inhabitants each. Whereas several decades ago most of the world's largest urban agglomerations were found in the more developed regions, today's large cities are concentrated in the global South, and the fastest-growing agglomerations are medium sized cities and cities with 500,000 to 1 million inhabitants located in Asia and Africa.

There is some level of degree of urbanization analysis for European countries.

There is also information the sizes of cities from counts of projected cities of different sizes.

Large cities currently account for 8 per cent of the urban population of the world. The number of such cities is expected to grow to 63 by 2030 and house more than 400 million people, representing close to 9 per cent of the global urban population. The proportion of the urban population concentrated in megacities and cities with 5 to 10 million inhabitants in 2014 varies widely across major areas, from 0 per cent in Oceania to 25 per cent in Northern America.

By 2050, the split of the urban population will be about 30% in cities of 5 million or more, 40% in cities of 500,000 to 5 million and 30% in cities of 500,000 to 5,000.

An analysis by small, medium and large cities will be more important than lumping all non-rural areas together.