They'll do it when two conditions are met: (i) the probability of success is high enough, (ii) the probability of success will decline if they wait. Basically,

They'll do it when two conditions are met: (i) the probability of success is high enough, (ii) the probability of success will decline if they wait. Basically, when China is at maximal power relative to the US. Most credible commentators in the West say that'll be in 2027.