You can see some amazing growth has occurred in these countries since 1980. The Dominican Republic went from just 1,000 members to over 100,000 members in 2006. Membership in Brazil and Peru increased by a factor of 10. Membership in the United States has also doubled in the past 25 years. It is likely that we will find the bulk of the future growth of the Church in these 19 countries.
There are areas of the world which have high potential to experience strong growth in the next 20 years. These countries are in Africa, South America, and Asia. These are listed in Table 1.
These growth projections are based on how membership in countries which have over 100,000 members behaved when their memberships were smaller as well as their growth rates for the past eight years. I believe that these projections provide an accurate view of what the distribution of Church membership will look like in the coming decades with the exception of Paraguay and Malaysia. I imagine membership growth in Paraguay will slow in the coming years considering 1% of the population is already a member of the Church and Latin American countries tend to grow much slower once around 1-2% of the population is converted. As for Malaysia, there is always the possibility that membership could reach over half a million in the next 20-30 years, but unlikely considering the vast majority of the rapid growth the Church is experiencing there is due to immigrants and the native peoples on the island of Borneo joining the Church.
The most likely countries that we will see strong membership (and congregation) growth are mainly Nigeria, Democratic Republic of Congo and Ghana. These countries resemble the growth seen in South America in the 1980s the most (even though it is not quite a strong as it was then).