Any population prediction that looks solely to rate of population indicators is going to fail. It is no different than trying to predict the weather based on past indicators. Several things must be taken into account.
(1) Population density. As density increases so do disease and crime and war. Each of these will reduce growth. (2) Arable land and land productivity. Without food the population will not grow and both these affect food availability. (3) Medical progress. As population grows, death rates will increase and life spans will decrease unless medical advances keep pace with population. (4) Mobility. Some people will move to less populated regions or move to regions that can better support larger populations. Emigrants, if assimilated, will balance out population growth differences.
Especially that Iranians/Pakistanis/Indians are Caucasians.