This question will resolve as YES if a human crewed spacecraft successfully lands on the surface of Mars and returns safely to Earth before December 31, 2040.
The mission must be launched by a national government or an organization backed by a government, and must be publicly announced prior to the launch.
The mission will count as successful even if it encounters minor setbacks or challenges, as long as the crew is able to land on Mars and return safely to Earth. However, if the mission is cancelled or delayed indefinitely before launch, or if it fails to reach Mars or return to Earth, the question will resolve as NO.
The use of unmanned probes and rovers on Mars will not count towards this question - only a successful human crewed mission will result in a YES resolution.
Apr 20, 11:18pm: Will there be a manned mission to Mars before 2030? → Will there be a manned mission to Mars before 2040?
Given the discrepancy of these forecasts, there is either (1) a huge arbitrage opportunity or (2) forecasters believe it is very likely that there will be a long delay (or failure) in the return mission back to Earth. p.s. I do think there should be a "return to Earth" added to this title.