A fourth movie, if the franchise is successful, could reunite the aspects of the first three movies:
Kyle Rayner (Jack Black) could meet a much-older Alan Scott, who now becomes Obi Wan to his Luke. Through Scott's help, Rayner discovers that the "collective willpower" or "souls" of the entire dead GLC is "stored" somehow in his ring. Through his ring he can commune with the spirits of the dead Green Lanterns, including his immediate predecessor, Hal Jordan, who guides him through the final battle with Krona when it seems that all hope is lost.
Oh, and one last thing: To tie it all together, it turns out that the mystical jade lantern is actually a "key" hidden on the earth several millennia ago by the Guardians of the Universe which has the power to restore the power of the Green Lantern Corps, which it does in the fourth movie. It can't restore the old GLs back to life, of course, but it does bring back the collective power of the now-deceased Guardians in order to enable new Green Lanterns to be recruited. At the end of the fourth film, Alan Scott leaves Earth to become the "New Guardian," now holding the power within himself and becoming the spiritual leader of the Green Lantern Corps in a similar way to the old Guardians of the Universe. Kyle Rayner returns to Earth and continues his career there, satisfied that he's no longer alone in his mission. Oh, and he bags Alan Scott's oriental granddaughter, Jade.
I know I'm dreaming and that none of this will be made, but it could be cool.
