Off the Island
We’ll learn that Vincent’s mom is alive in the real world, not dead on the island. She’ll be old as fuck now, but she’ll see Vincent’s lunchbox on the news or a photograph somehow, which will be the first clue in like 40 years that what happened in that town wasn’t all a weird dream or psychosis or whatever. Vincent’s might even have spent time incarcerated after being blamed for Vincent’s (and perhaps even some others’) disappearance.
I think that other people who have died on the island have gone back to the regular world, too. Most notably, Father Khatri. Maybe even everyone who’s ever died in town wind up back in the normal word, or maybe only certain chosen folks do. Or maybe only folks who die in certain ways. Whatever the case, my thought is that at least the most interesting folks who die in town (Khatri, Abby, Tom, Toby, etc.) wake back up outside of the town.
Some of them will think it was a near death experience, some of them will think it was a hallucination, some will think they went to literal hell and came back. What’s for certain is that some of them are going to be all “Kate, we need to go baaaaaack!”
Also, next season we’ll getting flash sidewayses, babyyyyy!
On the Island
They’re going to find Tabitha’s body next to the Bottle Tree, and it’ll be exactly like how Vincent found his mom. You know how he said to Tabitha that she must not have made it to the tree in time? I bet she did make it to the tree, and the boy in white or someone else shoved her out of the lighthouse in the exact same way. When Vincent sees Tabitha, he’ll put the pieces together. That’s will probably spur him to work more actively with Jade.
Of course, most people won’t believe him because nobody takes Vincent seriously. And Jim will be a big asshole about it because Jim is a big asshole. He’ll interpret it as Vincent giving Julie & Ethan false hope and being unintentionally cruel. Boyd and/or Donna & Ethan and/or Julie will believe him, causing a rift on the island.
All of the above makes me think that’s why the voices kept telling Sara the way to go home was to kill a bunch of people. They actually were trying to help. The more people who go back home, the more likely people off the island will find a way back.