The number of opportunities they have to actually pull it off are so few and far between just from demographics, geography, and meteorology alone, that you can count with two hands the exact number of days between now and when the window will basically close permanently when they could even hypothetically make an attempt at it without cursing their entire invasion force to the bottom of the sea before they even encounter a defensive line.
Not to mention the rumours that Taiwan has developed a non-nuclear MAD doctrine which would allow them to instantly turn 400,000,000 Chinese citizens into refugees by blowing the 3 gorges dam. A scenario that would require China to turn any deployed forces right around to institute martial law.