The only scenario I could see on China attacking Taiwan is if it declared independence, and since that train left the station in 1995/96, I don't believe it'll come up again.
As things stand now across Taiwan Strait, it's very difficult to imagine mainland China would use force to invade or unify Taiwan, barring some unexpected and unforeseen circumstances. Unification is the only acceptable outcome by the vast majority of Chinese people, but you don't and shouldn't achieve unification by force.
Most mainland Chinese consider Taiwanese compatriots and there is no deep-seated hatred across the Taiwan Straits. Growing Chinese wealth and power actually give China confidence and patience and make the war even less likely. The geographical, historical, ethnic and cultural as well as more recent economic and social links between the two are too strong to allow Taiwan to choose its own destiny separate from China.
While much have been made of some cold and dry statistics such as 40% of Taiwan's exports are to China, by far its largest market, over one million Taiwanese live and reside in China, or polls after polls says majority of Taiwanese prefer status quo versus unification, they hardly give people a good grasp of what's going on between Taiwan and mainland China. The following are some more interesting facts/figures/anecdotes that collectively paint a much more lively and real picture of the across-strait relationship:
1. Currently there are over 800 direct flights between Taiwan and 20+ mainland cities a week. There were none merely six years ago. In 2013, more than 2,850,0000 mainland Chinese visited Taiwan, a record, after Taiwan government started gradually accepting mainland tourists, with caps on daily maximum numbers. MOre Taiwanese visit mainland a year.
2. In 2012, the most recent figures available, four out of the ten top-paying cities at Taobao, the largest Chinese eCommerce site owned by Alibaba, are Taiwanese cities with Chiayi at No 1, Kaohsiung at No 3, Taichung at No 7 and Tainan at No 9. The bigger mainland cities Shanghai, Beijing and Shenzhen are at No's 4, 6, 8, respectively. The funny thing is, since most Taobao vendors offer free domestic shipping compared to charging fees on overseas shipping, many Taiwan buyers fill their addresses as "Taiwan province" causing much consternation among hard-line Taiwan independence supporters.
3. Xiaomi smartphones have become quite popular in Taiwan, with customer lining up to snatch the phones. The interesting thing to note is that many key component suppliers and the final assemblers are Taiwanese (operated in mainland or Taiwan), but the phones are designed and branded in Beijing. China's WeChat and Weibo are also quite popular among Taiwanese, to the point that some Taiwanese websites frequently list them on their "Share to" links.
4. Some mainland TV series become top viewing popular shows in Taiwan. Mainland entertainment programs have attracted large audience and followers in Taiwan - e.g., I'M A Singer where quite a few singers from Taiwan won the top awards and Taiwanese cheered and cried for their favorite contestants, calling for fairness and unfairness of the contest. All told: deeply and emotionally involved.
So what do all these mean when putting together? Well, Taiwan is integrated into China gradually and increasingly falls into China's orbit. If, twenty years ago, Taiwanese came to the mainland with wealth, technology and soft-power that the mainlanders looked up to, today, the influence is mutual and is increasingly shifting to mainland's favor.
The video clip below is from a popular Taiwan talk show; the guests were discussing the "invasion" of China's products, software and pop culture:
(Apology for the non-Chinese speakers here. The discussion is in Chinese. The guests basically talk about what I summarize above: Taobao, WeChat, I'M A SINGER and their implications for Taiwan. They're obviously "shocked and awed.")