WARNING: This article has Star Wars: The Last Jedi Spoilers.
What George Lucas’ had originally planned for Star Wars: Episode VII is quite similar to the story points used by Rian Johnson in Star Wars: Episode VIII-The Last Jedi. Lucas sold his company Lucasfilm in 2012 along with all its properties to The Mouse House and even handed over his story treatments for the Star Wars sequel trilogy. However, when J.J. Abrams joined Episode VII in 2013, he along with co-writer Lawrence Kasdan and the Star Wars Story Group discarded Lucas’ ideas and progressed on their own. Thus, The Force Awakens came into being.
The Force Awakens featured a girl called Rey who met a Resistance droid and a defector from First Order. They forged a team and worked in tandem with Han Solo and Chewbacca to deliver the map leading to the first Jedi temple to the Resistance. During the journey, Rey finds out about her Force-sensitivity and ultimately chases Luke Skywalker to train her. In the movie The Last Jedi, Rey starts her training under Luke’s supervision, although, the Jedi Master has come to believe that it is time for the Jedi to end. Eventually, he battles his former student, Ben Solo aka Kylo Ren and he manages to distract him for long enough to facilitate a Resistance escape. Luke Skywalker’s story came to an end in The Last Jedi, but, that was something which Lucas had originally planned for Episode VII.
The new book Art of Star Wars: The Last Jedi revealed that the first meeting to deliberate upon The Force Awakens story was held in January 2013 at Skywalker Ranch. During the meeting, George Lucas shared the concept art for an older Luke Skywalker, a young Jedi padawan called Kira (who was later given the name Rey), and a bell-style architecture for the first Jedi temple (it got redesigned later and was shifted to the planet Ahch-To). Although most of those concept arts were rejected, some have been featured in the new book. Have a look at the concept art for the first Jedi temple (art by VFX art director James Clyne).
The book also showcases the Episode VII plans of Lucas and probably the remainder of his Star Wars sequel trilogy. Eventually, Luke went into exile on the remote planet where the first Jedi temple was located, several decades after the Galactic Empire ceased to exist. During the movie’s course, Luke slowly got back his motivation and started training the new Jedi called Kira. However, that story failed to gel with the plans Abrams and Lucasfilm had for the Star Wars sequel trilogy. Thus, the story treatment was postponed for The Last Jedi, at least in bits and not as a whole.
Had Luke given training to Rey in The Force Awakens and not The Last Jedi, then the Star Wars sequel trilogy would have taken a different trajectory. However, Luke was the MacGuffin during Episode VII, and that enabled the various original and sequel trilogy characters to join hands in their search to find one man. Ultimately, everything fell into place. However, we will just need to wait to find out how everything is wrapped up J.J. Abrams in Star Wars: Episode IX.