Couple of things;;
First, I finished the damn book. On to the next! anyway, i still maintain that the Yuuzhan Vong aren't outside of the force at all, but are simply (and perhaps only) part of the Unifying force which, to this point, every jedi has pretty much been ignoring.
Living Force - The force which affects creatures/beings. Such as picking up a big fricken rock and throwing it, shooting lightning, jumping really high. 90% of the force which the Jedi wield seem to be about this.
Unifying Force - The more mysterious and less explored of the two, the Unifying is part of everything, and is more about your place in the universe and the fate of all beings.
But in any case...
Kyle Katarn ain't no Jedi Master. He's a Jedi instructor, and teaches the big kids how to fight with their lightsabers. He's no master, though. His abandonment of the force after defeating Jerec caused a bit of irreperable damage to his force ability. He's strong, plenty strong, but not a Master.
After Desann, in his 'official' storyline, it looks like Kyle goes straight for the Vong afterwards. After becoming a Jedi instructor, Kyle taught many of the Jedi students who later went off and got themselves killed at the worlds of Ithor and Obroa-Skai. Maybe he'll take up the saber again, or maybe one of his students will.
And IMHO, any game/expansion on the YV would sell just fine. Why? not everyone who bought JKII was a star wars buff. And even if you are, most actually like the YV.