The US has dominated military spending and still spends three times more than second place China in 2015. New projections have China defense spending in 2030 at about 66-75% of the projected US spending level. India could near 30% of the future US defense spending level.
The US will still be dominate especially as actual accumulated military hardware is based on purchases made over 10-30 years. The US will also have a training advantage, since military personal will have a lot of actual experience fighting in actual conflicts and wars.
By the 2030s America will still be the top power but a few others will have great power status.
A handful of significant countries with great power status is similar to the world of the late 1800s and early 1900s.
There will also be megacities and megaregions with 20 million to 300 million people.
China is not expected to match or exceed the US defence budget until 2025-2050. Even when it does match the annual defence budget it will take many years to develop comparable military capability. The UK will have one third of China’s budget this year but the UK has superior force projection and military capabilities.
The three major economic mega-urban zones are the pearl river delta in the south (merging into one 42 million person city) and Yangtze River delta around Shanghai and the Bohai economic rim
The area around Beijing and Tianjin, two of China’s most important cities, is being ringed with a network of high-speed railways that will create a super-urban area known as the Bohai Economic Rim. China is merging Beijing/Tianjin and several other cities around the Bohai Sea into one big super-urban zone over the next several years. By 2020 there could be 260,000,000 people (3% of the world’s population) in one big super-city.
India should also have more urbanization and creation of connected megacities and regions.
India has potential megaregions
* Gurgaon, Delhi and Noida.
* around Chennai (Sriperumbudur, Bengaluru )