Having learned from history, I can't see any major actors in the CPC or PLA seeking to liberalize politics in China for at least the next half century.
No, I agree with that. Some actors seeking to take bigger piece of the cake is more likely, especially if the cake doesn't grow as much as it did in the past.
China cannot learn from Russian history, this is the mistake the CPC made in the 1920s, and the CPC has been making since the 1990s. From the perspective of PRC history, repression has always had negative effects, but liberalization has been a great success.