That's not a guarantee at all. The only thing he's every been honest, consistent and truthful about is that nothing is sacred, everything's on sale, no values (economic, patriotic, environmental, political) will stand in the way of his own profit, there's always the willingness to make a deal and sell something (someone) off, and fuck the consequences, no matter how gigantic, embarrassing, and suicidally bad they are. Negative-sum deals are absolutely on the table as long as he comes out richer or more powerful.
China just needs to make a good offer and Taiwan's fucked when it comes to Trump's support.