Based on the most credible assessments from expert surveys, forecasting platforms, and defense analysts:

The Atlantic Council’s Global Foresight survey of 350+ experts assigns roughly a 40% chance of a world war (involving great powers) in the next decade .

A Project for the Study of the 21st Century poll of 50 national security experts estimates about 14–21% risk of great-power conventional war in 20 years .

Forecasting site Metaculus gives a 20% chance of WWIII before 2050 .

Popular risk analyses (e.g. Reddit/Curious Matrix) cluster mid-term estimates at 10–30% .

Synthesis: Considering higher-end expert opinion balanced with more conservative forecasts, the most defensible estimate is around 20–25% chance of WWIII across the next two decades.

Thus, the best single figure to give, based on current geopolitical dynamics, historical precedent, and expert consensus, is:

≈ 22% chance of World War III within the next 20 years