TID v0.99 Directors Cut with the revamped third act and an optional Harem ending is indeed expected by fall ‘25. Think of it maybe as a Christmas present.
As of now there is already a completed beta with most if not all content done being internally tested. They are now reviewing the updated script (it’s a LOT of work, more than 140k words), doing some rewrites and reshoots of older content animations. This was explained on a devlog not long ago. I believe it was copied here somewhere a couple of pages back. 
So the release is not yet imminent, but it seems to be on track for later this same year/early beginning of ‘26 at worst. Depends on how the testing goes ofc, but it looks good so far.
Changes are substantial, so im pretty sure old saves won’t be compatible and a new game from start will be required.