I know two Mainland Chinese Cantonese speakers, and neither of them consider themselves "not-Chinese". On the contrary, I've heard more that Cantonese-speakers view the language as being the more " authentic" Chinese. Guangxi actually has a lot of Canto speakers too. Improved linguistic rights are more likely, but the greivences that would induce seccession don't seem to be there, especially in 1989-91, so it would probably not even be an issue to be addressed till later down the line, when the proportion of Mandarin speakers increases with China's economic growth.Everyone has offered the classic gripes with this map, but lets say we do want a realistic balkanized China, what does that look like?
If we want to take it really far, we could see regionalism in economically powerful regions which want to break off from an economically collapsing country, perhaps. Places like Guangdong COULD potentially then back-justify this by saying that Cantonese speakers are a distinct ethnicity and thus deserve a nation state, but Id need people who know more about China to tell me if thats even remotely viable.
Manchuria and inner Mongolia re staying almost certainly. If you REALLY want ethnic separatism, MAYBE a Zhuang state though I imagine that's economically a bad idea, I doubt they have much to work with in inland Guangxi.
The Zhuang don't seem to have any problems with the CCP that would lead to seccessionist feelings, especially in 1989, as the regime was more conciliatory with ethnic minorities. Otherwise, we would've heard about it. A lot of minorities were/are pretty well assimilated into China and Chinese society owing to longer periods of Chinese rule. The ones that arent are the ones we know. (Tibetans, Uighurs, Mongols to a much lesser extent)
Realistically, only Tibet and Xinjiang have the best chances, but even then, Xinjiang would probably be a war zone owing to the large numbers of (armed) Han living there.
My biggest gripe with independent Xinjiang borders is that they go off of PRC-drawn boundaries, which in turn reeks of "lets balkanize China by removing provinces marked differently" and ignores realities on the ground...