China is now pushing the idea that Taiwan will be peacefully (with perhaps a bit of military threat) taken over by 2021.  There has been much speculation that China might make an attempt to capture Taiwan, using military force, sooner. But a closer examination of China's military power indicates that it will be many years, a decade at least, before China could be capable of  taking Taiwan via an air, land and sea campaign. But then there is the possibility of American intervention. Even 2020 might not be enough time for China muster sufficient force to take on American military power. Increasingly, the Chinese leadership is taking the longer, and safer, view. This is in contrast to the saber rattling from some generals and other officers. 

China also has an ancient problem with peacetime rot. The military becomes less effective during long periods of peace, but the generals are not aware of how poorly prepared their troops are. China last fought in 1979, against Vietnam, the military performed poorly.   

Taiwan is taking the Chinese threat seriously, and considering moving some of the eight military air bases in western Taiwan, to the eastern side of the island. This would make the air bases less vulnerable to attack by Chinese amphibious troops. But everything on Taiwan is vulnerable to air, with the west coast reachable within ten minutes by warplanes flying from China.