The relationship between China and Taiwan resembles the relationship between the US and Cuba: both situations involve a large island off the coast of a much larger nation with a significantly different political and economic system. In both cases, the island has been a major thorn in the side of the larger nation. The difference, however, is that no one claims that Cuba is legally part of the US.
Ten or twenty years ago, it was relatively easy to imagine the Chinese and Taiwanese governments agreeing on a formula by which the Republic of China would cease to formally exist for purposes of dealing with the outside world, but would retain considerable autonomy for domestic purposes. Since then, however, the independence of Hong Kong has been eroded, a significant portion of the Taiwanese population has embraced independence as an ultimate objective, and the Chinese government has become more repressive at home and more assertive in the South China Sea. The odds against a peaceful solution to the issue have grown accordingly.
The costs and risks of taking or annihilating Taiwan currently outweigh its benefits, from the perspective of the Chinese leadership. That situation is unlikely to change in the foreseeable future even if Chinese military power and assertiveness continue to grow at their current rate. On the whole, therefore, the prospects for a satisfactory negotiated solution for the Taiwan issue, while not good, remain better than those for Hong Kong.