All the other companies are adding features, stability modes, super slow mo, as mentioned before better colours and contrast.
Go pro are just throwing all their money on the engine.
For example sony have released a watch that controls the camera and has a screen which shows what you are recording.
I know the go pro can probably do this with an app on your phone, but this is on your wrist. No pissing around draining your phone, dragging it out of your pocket.
If your out kite surfing or diving you can't pull your phone out to check what's going on.
The other companies are seeing there's money in this racket, and will eventually back go pro's NUMBERS with extra features.