When prophecies go wrong, you can bring them up again later! There's still a chance that something new will happen to satisfy the prophecy in a way that makes you think, "Ohhh... it wasn't about that earlier thing at all. It was actually about this later thing all along. Now it all makes sense!"
In other words, you can just as easily apply the "Nostradamus post-hoc justification" to prophecies in games as some people do in real life. Our real world provides us with plenty of examples of people going out of their way to justify apparently mystical/supernatural events as real, so there's no reason you can't use the same tricks in a game.
Commentary by Keybounce (who has not seen the movie)
[Keybounce's comments will appear here when received.]
Commentary by memnarch (who has not seen the movie)
And there's the other key part for these being glasses; they're removable. They really looked like they were embedded in Kanata's face for a time there, what with the large, not-actually-eyesocket spots the lenses stay on. A curious design to have human sized eyeballs with the rest of the face. I guess Kanata also doesn't need them to the extent I need mine anyway; I would have a hard time seeing Rey clearly that far away.
A restoring imbalance second half? This sounds like something the Irregulars would make for the comic. It plays well into the 30 years later thing for the new characters, plus it's completely dialogue so no need to worry about it being contradicted by what's shown. However, the original prophecy didn't make that much sense (or even happen?), and this also feels like the sort of thing that a director wanting to make Star Wars bigger/better would add in to have a tie-in while "fixing" it. Plus, nothing would stop this from being an actual second prophecy rather than a continuation. If I had to pick one or the other though...... really close call, but an Irregular creation feels slightly more likely. The Orb worked out really well as a plot item, even if it only appeared once.
Darth Kanata: That laser sword. It calls to you.
Darth Kanata: There used to be a prophecy. Of a Chosen One who would bring Balance to the Force.
Rey: And that was a bad thing because previously good ruled. Balance brought back evil.
Rey: I know. Anakin was my grandfather.
Darth Kanata: Really?! Then you should know there’s a second part to the prophecy. About one who will restore imbalance.
Darth Kanata: If you’re Anakin’s granddaughter, that one could be you.
Rey: What about my mother?
Darth Kanata: Eh. Prophecies often skip a generation.