My Vietnamese friends, I think Taiwan is a lost cause. I have a very good friend from Taiwan and had hours and hours of conversation on this issue over the years. His opinion is that Taiwan will eventually unify with PRC, some day, it is a matter of when, not if. It is because most Taiwanese are migrants from mainland China, except for small percentage of indigenous population. As soon as PRC become more democratic and prosperous, then it will be in the mutual interest of PRC and Taiwan to create some kind of union, like it happened in case of Hong Kong and Macau.
This is just my honest opinion and I could be wrong about that. This is why I excluded Taiwan in the ASEAN+ regional union road map.
Currently (2010), mainland China has 3 provinces (out of 31 that are directly controlled by CPC, excluding Macao and Hong Kong) that have GDP surpassing Taiwan. Mainland China has about 25 times the GDP of Taiwan
If mainland manages to have 10 provinces that have GDP individually surpassing Taiwan, the people of Taiwan would lose completely their economical superior complex against the mainland.
At that time, mainlands GDP would be probably 50 times of Taiwans, though GDP per capita is still lower.
This may take 10-20 years to happen and is absolutely possible.
Politically, if the mainland becomes partially democratic with Taiwan politicians having certain say in mainland system, there is no reason the two armies cant unite against external threats: simple, if mainland can sign a mutual defense treaty with N Korea, why would not with Taiwan?
Such a democratic and united China could be a real nightmare for neighboring countries,
because we all know democracy is about money and emotion. A China then would have a huge pool of money, immense human resources, pretty high tech, and very nationalistic emotion.
If Taiwan politicians dominate China political arena, as a nature of democracy, and if you know ROC claims the whole Mongol, part of the N Korea, part of Vietnam, part of Burma, part of India, part of Russia, part of Kyrgyzstan, part of Tajikistan, some sea rocks with Japan and S Korea, and the whole of South China Sea, no soft tone could be expected.
Really I dont the vast herds of fools in India and Vietnam would push or otherwise wish for a democratic China, unless they are tired of their good days with current weak Chinese Communist Government.