The games creative director, Chris Esaki says,Ray Tracing technology really exposed a lot of the issues that we had and how we were either building the content or rendering the content. So its not just that Ray Tracing is coming to Forza Tech, its actually that a whole host of other technology around how were improving car models, and how were improving the track visuals, environment visuals and character visuals, just to make everything just beautiful and really pop in the scene.
Source: N4G PC Forza Motorsport 8 Will Go Back to the Series' Roots; Creative Director Talks Ray Tracing in Forza