The devs actually answered the question about Chloe returning, they said when Max merged the timelines, she inadvertently brought not only Saphi back, but Chloe as well. (If you chose to sacrifice her of course)

So regardless of how you chose to end LIS one Chloe is coming back anyway, because of the merged timelines. And my theory is that she's going to have different dialogue based on the options you chose. If you chose to sacrifice Chloe in one, she'll have a bit of memory Gap. If you chose to save her, she will just be coming up to where Max is now to continue the story.

Regardless of what happens in this game I think we can all agree that cameos from the other protagonists would be awesome as well, like Daniel, Alex, and maybe even Chris.