Speaking to VG247, Turn 10′s Dan Greenawalt says that they are using 100% of the Xbox One hardware, with plans to become more efficient as the console becomes more familiar.

 

It’s funny, because I hear it a lot: ‘are you using the hardware?’ The truth is, you always use 100% of the hardware. You just do, but it’s a question of whether or not you’re using it efficiently, and so that’s what happens over a course of years…Between Forza Motorsport 2 and then three and four, the game got incredibly technical. The hardware didn’t get any more powerful, but we got more efficient at doing our math. We’re using 100% of this console, but obviously we will become more efficient over the years.

 

 seems like what the Forza 5 team are saying is that they are using as much as they know about the Xbox One console pre-launch to make their game run at hardware capacity. Just like how Xbox 360 games began to look better and better as the years went by in its premium life cycle, Xbox One games made by Turn 10 and others will look better as dev teams become more and more efficient.