| Okay, a few things about the Yuuzhan Vong. First off, it's not that they don't exist within the Force, it's that they don't exist in the normal way within the Force as the Jedi know it. Anakin Solo in one of the later books discovers that he can sense them by looking for them on a different "branch" of the Force (assuming that the Force as it is known is one branch of a greater tree). He has to use some sort of crystal of theirs to let him see the branch... if I recall correctly, he gets a hold of the crystal to fix his lightsaber and a little later discovers the other use for it.
Secondly, they don't actually originate outside of the Starwars galaxy, they simply left for several thousand years. Their homeworld is the living planet Zonama Sekot, which is somehow capable not only of speaking with visitors (such as the Jedi who find it in the New Jedi Order series) but also of travelling through hyperspace (with unpleasant effects on the ecosystem of the planet). The planet actually was visited by Anakin Skywalker and Obi-Wan Kenobi before the Clone Wars and Anakin's fall to the darkside. Because it is capable of moving around, the planet is not well known, but there are some who know about it even after the Empire.
As far as people not knowning about the Vong before their invasion of the New Republic, that also is not exactly true. Most people didn't know about them, but a species living in the Unknown Region, the Chiss (Grand Admiral Thrawn is one of them, for those who've read the Thrawn Trilogy), were well aware of the threat and were actively working to keep the Vong from invading even before the rise of the New Republic.
If Kotor III were to take place away from the Core Worlds, and involve a war between nonRepublic forces and the Vong, it would certainly be possible to work it into canon. The only problem I see, doesn't involve the Republic, it involves the Vong themselves. In the NJO, they seemed to have only recently rediscovered the galaxy and actually thought it was a new one (sort of like Planet of the Apes, they left, they came back, they thought it was new), so I'm not completely sure how they would just "forget" for a few thousand years... maybe the Jedi Council could give them a mind wipe.
On the other hand, and I can't remember this exactly, I believe they were forced to leave their homeworld and even their home galaxy. If the battle in Kotor III was actually the one that made them leave in the first place, well, I suppose that could work.
Personally, I doubt that the Vong will have anything to do with the next game. Canderous mentions them in passing, sort of a little nod to the book series (which was still running at the time), nothing more. If we're lucky we'll see 'true' Sith (whatever that means) in the next game and they'll be just as scary looking as the Vong.  |