Here is a Nextbigfuture infographic with a projection of military spending in 2030.
This is mainly based upon IMF forecasted GDP projections to 2022 and then extrapolated to 2030. The 2016 military spending as a percent of GDP is assumed to still be used out to 2030. A country spending 2% of its GDP on its military or 5% of GDP is assumed to still be spending the same percentage in 2030.
Nextbigfuture believes the IMF GDP forecasts out to 2022 for Russia and Saudi Arabia could be high.
Also, China’s currency improved in 2017 and 2018 and has had strong GDP performance. Nextbigfuture used these adjustments for an increased forecast for China’s GDP in 2030.
Most of the countries are growing at near the same pace. China and India have more growth and so have bigger economies and more military spending in 2030.
The United States still dominates world military spending.