I'm thinking that we will have 2 releases before the ending release(s). One each for the Sandra and non-Sandra routes. That would fit in with their release-numbering scheme: v0.98 for Sandra and v0.99 for non-Sandra. Of course, it could also go v0.98, v0.98.5, v0.99, v0.99.5 if there is a lot more content they want to add. But I really doubt it.
Then again, we could see v0.99.001, v0.99.002, etc. if they want to really drag this out.
I am afraid that neither Lisa nor Dianne will get significant time (if any) in the rest of this game. It appears to me that the developers have decided to pare down the possible ending scenarios.
And right, there are no chapters in this game.