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[Star Wars] What would have happened if Obi-Wan Kenobi had escaped the Death Star alive?

Let's assume group escapes without needing Obi-Wan to distract Vader. Obi-Wan goes to Yavin IV with Luke on the Millenium Falcon as the Death Star approaches. 

How do the events of the series unfold from there?
gpt
Obi-Wan and Luke both pilot X-Wings during the Death Star assault.  Vader barely makes it out in time to survive the explosion, but is in no shape to dogfight Luke or Obi-Wan.  Wedge survives.

Luke still heads out on Hoth, but being more adept in the force, the wampa attack is detected sufficiently in advance that it becomes a simple dismembering from tauntaun-back.  Luke reports in that there are space-bigfoots about.  When Han reports that an imperial probe blew up, Obi-Wan immediately declares that they must abandon Hoth.  As a result, Vader's fleet arrives to find an empty and abandoned Hoth.

Obi-Wan and Luke both go to Dagobah, and Luke's training isn't interrupted to save his friends since... they don't need saving.  Luke manages to become a full Jedi and divines on his own that Vader is his father.  Yoda and Obi-Wan teach Luke how to handle force-lightning.

Return of the Jedi plays out pretty much the same, except that Luke easily bests Vader in combat without succumbing to anger, and isn't immediately roflstomped by Palpatine.  Sensing a real chance at victory, Vader turns on his master (this was his plan as indicated in Episode II) and the two of them dismember the emperor without much incident.

Vader fails to take command of the Empire, and is unwilling to join the rebellion.  Yoda still dies from space-flu.  The empire, without a strong leader, begins to unravel itself and an emergency senate is created in a final hope to restore order.