Everything, because it's much more likely that the number of games Hirai mentioned are merely PS VR compatible, meaning that they'll run on a vanilla PS4 to begin with.
That doesn't change my point. I'm talking about VR games that are only VR games to start with but are designed in such a way they could actually be sold as ordinary PS4 games if Sony felt they needed some extra content here and there. Let's say Horizon: Zero Dawn gets pushed back to 2017 and Sony needs something to fill that spot. Perhaps two VR games playable on the ordinary PS4 would be perfect (depending on what they were). Not only does it give Sony some leeway to adjust release dates but it also gives developers a chance of making more money on older VR games.
Sony are no longer competing with MS, they competing with the PS2 and they'll want to keep that momentum going.
The PS5 Exists.