So after the revelations of 3D, I feel like this line now has double meaning. For all original intents and purposes, Destiny Islands' keyhole was invaded by the heartless and the world was destroyed. In light of the time travelling reveal, perhaps the brown-cloaked figure also meant that this era of time has been connected to wherever else this figure may have traveled. At different points in the series the word "World" has sometimes referred to the entire universe of kingdom hearts worlds. Maybe i'm overreaching, but I feel like the "world" the brown-cloaked figure is referring to could be this part of the timeline where Ansem SOD is threatening all of existence. This doesn't really impact too much of the series plot that I can see, but I thought it was interesting that something very early in the series can be entirely reinterpreted.