In Xi's speech, which came on the 40th anniversary of a 1979 Chinese Communist Party (CCP) policy statement titled "Message to Compatriots in Taiwan", he called the integration of Taiwan and China a "historical conclusion drawn over the 70 years of the development of cross-strait relations" but offered few new specifics.
Xi's words that Taiwan "must and will be reunited" follow along with Beijing's long-standing view on its most sensitive issue, though there is some worry in Taiwan that with his increased power Xi is in a stronger position than his predecessors when it comes to achieving this goal.
Tsai, responding to Xi's speech at a Wednesday afternoon press conference, said Taiwan would "never accept" such a framework.
But it was when U.S. national security adviser Zbigniew Brzezinski met then paramount leader Deng Xiaoping in 1984 that the idea of "one unified country of China with two systems" was first floated to resolve the Taiwan dilemma.
The arrival marked the first time Taiwan has received 11 million overseas visitors in a single year, following 10.7 million visitor arrivals in 2017 and 2016, and 10.4 million visitors in 2015.
In a policy speech centered on Taiwan, Xi said, "We are willing to create a vast space for peaceful reunification, but we will never leave any room for any sort of Taiwan independence separatist activities". But what does it mean for China-Taiwan relations?
Though Xi insisted that "it's a legal fact that both sides of the Strait belong to one China, and can not be changed by anyone or any force", his speech was to some degree conciliatory, calling for discussion and increased economic cooperation. The two sides have been ruled separately since Chiang Kai-shek moved his Nationalist government across the Taiwan Strait during the Chinese civil war.
Apart from keeping up the pressure on the Tsai administration, President Xi's speech was also a warning to the United States, which China worries will leverage the Taiwan issue to force more concessions from the Chinese.
In his speech, Xi mentioned the so-called "1992 consensus" twice and included "national unification" as part of his definition of the "consensus".
Should mainland Chinese indeed flock to Taiwan in 2019, tourism operators in KMT-led cities and counties could see significant increases in revenue - which will inevitably lead some to attribute the gains exclusively to the KMT's attempt to warm relations with Beijing, while overlooking ongoing efforts to attract tourists of other nationalities under the New Southbound Policy.
China, meanwhile, has sought to isolate Taiwan under Ms. Tsai, freezing official cross-straits communication, increasing military exercises around the region and persuading a series of diplomatic allies to cut ties with Taipei.
Xi proposed talks between the two sides to work out "a systematic arrangement for the peaceful development of the cross-strait relationship". Last year, China also forced global airlines to change their websites and no longer list Taiwan as an independent country.
All people in Taiwan must "clearly recognise that Taiwan independence would only bring profound disaster to Taiwan", Xi said.