Mercedes has made .7 second improvements from the power unit alone year on year. The fact they need so much less fuel than everyone else is a huge advantage, even if they make no power gains they're still ahead. But you're right, I suspect hunting for those last 30 or 40hp is going to get difficult from here on in.
There's a theoretical 1,000hp that's possible, everyone is now at least within 92% of that figure.
The height of cultivation is really nothing special. It is merely simplicity; the ability to express the utmost with the minimum. Mr.Lee