You are aware that Denning is writing another trilogy that takes place in the galaxy after NJO, right?. The whole thing with the NJO was moving towards stories that take place within a bigger galaxy rather than in a self contained trilogy.
As for the ending being unfulfilling, I look at it being more realistic. People in the GA now have to live with the Yuuzhan Vong, same as those in the NR had to live with the Empire. The same way people had to live next to German's after the two World Wars.
EDIT typos