Originally posted by: ShiftyEyes
Personally, I think it's fair to say that when George Lucas created Star Wars, he had a rough story idea, more or less with basis in Kurosawa's The Hidden Fortress. He tosses in some Flash Gordon and Buck Rogers, and Star Wars was born. He thinks up a pretty rich (though not necessarily specific) backstory concerning the Jedi Bendu, the nature of the Force, mythical wizards, etc. Throughout the development of his script, he pares down all the backstory and we get what we know today as Star Wars (A New Hope). Lucas had intended the film to carry on in the tradition of old serials, so he envisioned a series of cliffhanger type entertainment. He tries a story treatment for the second film, perhaps bringing in more of the mythology he created (kyber crystals, etc). He eventually tosses this idea (Splinter of the Mind's Eye) and decides to continue the story in a more traditional means. The concept of The Empire Strikes Back is born. Lucas figures he could throw in a real twist and combined the Anakin and Vader characters. At this moment, he envisions a more detailed backstory (with Anakin & Obi Wan, the old Republic, plotpoints, and all, but still fairly rough) and figures he could make a prequel trilogy. He's also young and figures Star Wars could thrive as a James Bond type series, so he reasons that he could do more trilogies in the future. Around the time of Return of the Jedi, he probably gets tired of it and decides to make the third film the big finale. He ties up loose ends even if not according to the original plan for the sequels (like Leia and Luke being siblings) and puts a cap in the series for a while. Then his wife divorces him, takes half of his money, and he spends the next decade or so making it back with merchandising, producing movies, etc. He also keeps an eye on technology and when it's right (around the time of Jurassic Park), he decides to start on the prequel trilogy. While he has a rough idea of where things will go, it tortures him to write the scripts, but he eventually does it and attempts to once again wrap things up.
That's all conjecture, but I think it's reasonable considering what we know and what Lucas has said in the past.
Agreed. I believe we can surmise more beyond that, but that's still a good starting ground.