It's entirely possible that Jacen describing Ezra and Thrawn's galaxy as "far, far away" is nothing more than a simple Easter egg intended to light up the part of viewers' brains that gleans satisfaction from recognizing things. It's also possible that this particular phrasing is intended to clue viewers in to just what might be in store for Ahsoka when she presumably arrives in this new galaxy.
The original opening crawl is most likely describing the galaxy in which "Star Wars" takes place as being far away from the Milky Way, as if a storyteller is recounting the events of "Star Wars" as history relative to Earth. Keeping this same distance in mind, then, would suggest that Ahsoka will meet Ezra and Thrawn in our very own Milky Way galaxy. Some fans have floated this theory online with varying degrees of seriousness, like Twitter user @preston__tano, who added an "lol" after bringing up the possibility. User @jtimsuggs likewise joked, "Imagine if the other galaxy is Earth and Ahsoka and Sabine just end up at a Denny's in Chicago."
In all likelihood, Ahsoka is going somewhere new and not simply near Earth. Nevertheless, Jacen's line seems to be hinting at the possibility, even if that hint ultimately amounts to nothing.
