Last Warning Huge Spoilers from Star Wars Legacy of the Force: Betrayal...
Wow what an ending. The Sith have returned and another Jedi has fallen, how many is that now? Anyway, among the many thoughts I have about the book and its ending one in particular sticks out. Jacen foresees that he will face Luke and strike him down if he lets Nelani capture Lumiya. Even though Jacen stops Nelani, my question is will Jacen's vision come true anyway?
Before I give my answer let me take a step back. Consider another fallen Jedi that attempted to stop his premonition from becoming reality - Anakin Skywalker. Anakin foresaw the death of his mother. He failed to act before it was too late. He also foresaw the death of Padme. He took action, stopped Mace Windu from executing Palps and turned to the Dark Side to gain the power to save Padme. Ultimately his actions do not prevent Padme's death.
So, will Jacen stop his premonition of Luke's death or will he fail as Anakin did? I think that Luke will survive and Jacen's vision will not happen. Why do I believe this? For starters, Luke had his own vision, of an enemy "who does not exist". By the end of the book Luke had a vision that his enemy "does exist". This enemy is Jacen Solo who has given into the Dark Side. I assume that because Luke's vision has changed by the end, and the enemy is real, that Luke will take more direct action against his vision. I think Luke working against his vision will work in Jacen's favor. In Anakin's case, none of the Jedi shared a vision that was connected to his vision of Padme's death. In addition we know the asteroid where Lumiya took Jacen is taken is full of Dark Side energy. It's possible that the presence of the Dark Side energy could have been manipulating Jacen. It's possible that Jacen's vision may have been a deception to get him to turn to the dark side.
I admit all this is a stretch, and hopefully I did not miss any clues in the book. Since we have to wait to find out what happens, might as well speculate.
May the force be with you!