Many speculate that Luke's death will be revealed at around the end of the Fate of the Jedi Series. The Series deals with Luke being exiled, and he and his son Ben, go in a search through the galaxy to uncover what caused Jacen to turn to the dark side. (Or better, to uncover what caused him to break.) The Series just started, and book 3 is coming out this August, (the whole series is going to consist of 9 books.) I suggest you read them, there really good.
It is a known fact that Luke dies though, sadly. It is proven when Luke's force ghost appears to Cade Skywalker in Legacy. But Luke may have been killed by Lord Starkiller in Star Wars:The Force Unleashed:Ultimate Sith Edition since Luke battled Starkiller(Vader's secret apprentice)who is really Galem Marek, son of Master Marek.
As a side note, during the New Jedi Order series of novels, the writers were planning to kill Luke Skywalker in the book Star by Star, however George Lucas intervened and indicated that Luke was not to be killed at that point, so they wrote the death of Anakin Solo instead