I know of no other case of an authoritarian regime being successful when ruling over a large, dynamic economy. The USSR lasted 70 years. China is pushing that right now, although they might get extra life, because they have been able to liberalize a lot more than the USSR ever did.Generally political systems are fairly stable when either on the more authoritarian or the more democratic side.
Soviet was a "communist" dictatorship, modern China is a ultra capitalistic dictatorship. That's the difference. Also USSR poured insane amounts of GDP into the military, where China doesn't (or I should say, as far as we know they don't). China will prevail, may cause a lot of suffering for 10-100 millions but the new empire will most probably not fall.