There's no scenario where China doesn't get Taiwan, unfortunately for the people there. The only question is what that's going to look like. The rest of the world will do nothing about it, other than wave their hands around frantically. When it happens (during Xi's lifetime), it's going to set a particularly terrible precedent that will encourage Russia to do more of the same in eastern Europe. If China then decides Mongolia too is part of greater China, who can really stop that? Nobody.