SpaceX switching to hot staging instead of the flip maneuver:
There have been hints for a while, as people spotted a ring piece with strange cutouts that was hard to explain otherwise:
Supposedly, it gets them 10% mass to orbit. The original flip maneuver fits with Musk’s philosophy of “the best part is no part”, and hot staging will require something more than that (if only thermal protection for the upper part of the booster). But it’s still pretty simple compared to the usual approach of pneumatic pushers and the like.
It also potentially adds escape capability. If the upper stage can separate like this, there’s a possibility it could do so under more adverse conditions.