Looking at timelines for the expanded universe (link: Star Wars Expanded Universe - Wikipedia, the free encyclopedia), and going off of how long it's been since these three were last in a Star Wars movie (30 years), I'm going to guess we'll be dealing with the Yuuzhan Vong. If that's the case, well..... *grabs camp chair and gets in line at local theater*
If they go that route, it will be interesting to see how the death of Chewbacca is received.
"Greetings, Starfighter! You have been recruited by the Star League to defend the Frontier against Xur and the Ko-Dan Armada."