When Star Wars: The Force Awakens hit theaters in December 2015, fans finally got to see a very brief glimpse of Luke Skywalker (Mark Hamill), who had been absent from all of the marketing materials leading up to the release. The final moments of the movie showed Rey (Daisy Ridley), Chewbacca and R2-D2 flying to the hidden planet of Ahch-To, to return Luke Skywalker's lightsaber. We know that Star Wars: The Last Jedi will pick up exactly from that moment, but as it turns out, director Rian Johnson asked The Force Awakens director J.J. Abrams to slightly change this ending, to help set up his sequel.
The productions of both The Force Awakens and The Last Jedi both slightly overlapped, with The Last Jedi starting production just as The Force Awakens was wrapping. When Rian Johnson learned about what J.J. Abrams was planning for the ending, he asked J.J. Abrams for a small favor, which resulted in Rey getting R2-D2 as a travel companion to Ahch-To, instead of BB-8. Here's what the director had to say to Entertainment Weekly.
"Yes. The big [favor] was, I asked if R2 could come with Rey, and if BB-8 could stay behind with the Resistance. Originally it was BB-8 who went with Rey, which makes sense for the story in a way. But I asked, 'Can you do me this solid and switch the droids?'"
Throughout most of The Force Awakens, R2-D2 remained in sleep mode until the opportunity arose for this droid to reveal the final piece of the puzzle that unlocked Luke Skywalker's hidden location on the planet of Ahch-To. Rey was also accompanied by Chewbacca in the Millennium Falcon, with a report from last year revealing that both Chewie and R2-D2 will be living in the Millennium Falcon, keeping watch for any intruders since Luke Skywalker's location has been compromised. However, Luke is said to have found an important clue on Ahch-To and isn't ready to leave quite yet. Naturally, none of these details have been confirmed quite yet, but Rian Johnson did add that, although he only appeared in one scene in The Force Awakens, Luke Skywalker will have a much bigger role in Star Wars 8.
"Figuring out where his head was at was the very first thing I had to do when writing the movie. I had to crack this. And it had to be something for me that first and foremost made sense. Why did Luke Skywalker go off to this island? That was the starting point, and that's what the entire movie explores."
As for BB-8, he will be seen alongside Poe Dameron (Oscar Isaac) in Star Wars: The Last Jedi. When asked why Luke fled to Ahch-To instead of staying and fighting Kylo Ren, Rian Johnson revealed that he wanted there to be a good reason for why he left that makes sense to both Luke himself, and the audience. It remains unclear when the next trailer for Star Wars 8 will drop, but hopefully we'll get to see more of Luke Skywalker at that time.