Their government's current history is measured in decades. Future historians may yet measure it in decades. Do not be so quick to praise tyranny. It will last until the economy plateaus. Only then will we see if it is resilient.
No civil war destroyed all records. No civil war spanning more then three generations. No locked in against foreigners syndrom.
If China does undergo civil and political upheaval I don't think it has the social institutions or mechanisms to suddenly switch to enlightened liberal democracy, history matters, but that doesn't mean the Communist Party is guaranteed political control in perpetuity.
It got pretty damned close in the Cultural Revolution.