Russia didn't need to invade Ukraine either.
But nonetheless China is clearly preparing itself to be ready to be able to invade, with aircraft carriers, amphibious assault ships, dual purpose roll-on/roll-off carriers. It doesn't mean it will, but that it wants to be able to.
So basically it will depend on a single dictator's whim if they do or don't.
> Establish a total naval and air blockade of Taiwan using their fleets stationed in Ningbo and Zhanjiang
Which would be considered an act of war, so it's the same scenario again.
> There is a substantial opposition in Taiwan that want reunification (~20% of population support directly Li-Wun)
20% is more than the % of people in the Donbass that wanted unification with Russia, and we can see how well that went. And it wasn't a dangerous amphibious assault against an island with shit terrain.