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.
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.
Here is translation of a plan for the development of the Bohai Economic Rim.
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 )