50-50? My most likely unification scenario is not so much a Chinese invasion, as political surrender by Taiwanese politicians, cast as a “peace agreement.” How exactly this would affect the system here is an interesting question. For example, if the ROC government simply conceded that it was “part of” the PRC, but otherwise continued functioning as before (perhaps relabeled), then that wouldn’t by itself give us a Hong Kong type system, where the PRC is able to manipulate the semi-democratic system through appointments and court decisions. They’d still have the tools of bribery / patronage and media domination, of course, and will have amassed enough data on individuals to intimidate many of them.
(In the past, I understand that China has offered Taiwan an agreement whereby Taiwan would keep its system of government, and independent military.)
Otherwise, we might still have a stalemate in which the USA, and perhaps also Japan, continue to counterbalance China. Or China could…if not exactly collapse, then at least be seriously weakened by such macro-level difficulties as demographic aging or economic stagnation. Some sources speculate that this is likely to happen in about a decade.
My worst-case scenarios are unrelated to unification: nuclear accidents here, or on the Chinese coast, that turn Taiwan into another Chernobyl; a volcanic eruption (probably in Indonesia) that changes world weather; spiraling global economic collapse…