I don't think people are completely understanding my version of events. Luke sees Obi-Wan, Yoda, and Anakin's ghosts. The the three old ghosts morph into their younger selves. Then Luke leaves with Leia to join the celebration. Then Qui-Gon appears besides the young Obi-Wan, Yoda, and Anakin. (Notice that Luke does not see Qui-Gon, because as everyone is so quick to point out, he would no know who he is.) Then we see the original final shot of the OT characters with the Ewoks. Then a NEW final shot with the four ghosts: Anakin, the main character of the saga, his mentor and brother in arms Obi-Wan, his father figure (as well as Obi-Wan's mentor) Qui-Gon, who first discovered the path to immortality, and Yoda, ultimate Jedi Master and mentor to them all. This isn't for Luke, it's for Anakin (the main character of the saga), and the audience.

As for Qui-Gon, the plan was to have him dissapear in the flames. There is an in-depth discussion about Qui-Gon and his role in the prequels/saga in the Shroud of the Dark Side thread.