Most of the stuff the summer update is adding:
- Terrain painting, shrub tools and scenery items like rocks and individual trees
- Wetlands with a wetland requirement for Spinosaurids.
- Fish feeders which Spinosaurids will primarily feed on.
- Pachycephalosaurids can engage in fights against small theropods, with finishing animations.
- Expanded gyrosphere features (can build tracks through enclosures now).
- A few other changes to dino behavior.
- Challenge mode additions
- Misc quality of life features like more building info, details on power consumption, etc.
There's also a paid DLC coming later on.
So far none of the stuff in the leak apart from the carnivore DLC has been confirmed, but it probably will when we know what the DLC is.
Decent overall, but this is something I would have expected six months after launch, and not almost a full year later.