You know, the early 2000s looked pretty promising, with China and Taiwan having normalized relations for a while and with cross-strait business blooming. Back then a large portion of Taiwanese identified as Chinese. Today's tensions haven't always been there. As little as 10 years ago, Taiwanese supported reunification (though on their terms, e.g. the ROC government takes over the mainland)

Ironically, Taiwan is very pro-Japan nowadays even though Japan was a colonizer in the early 20th century. Given this, it's not at all set in stone that relations will stay bad if peace endures.