If the US is poised for full on dictatorship, it makes sense to go in early.

If there will be a change in leadership, it makes sense to wait until the US has weakened every alliance as much as possible under Trump and then invade quickly like what Russia did.

Xi has demanded that China be "ready" in 2027. So he seems to think that China will not be militarily capable of doing so before then. (Or at least he seems to be saying that. It could be a misdirection.)