Turn 10 have just posted on their website that Le Mans will be returning to the Forza Motorsport series in Forza 5 in not only the seen previously La Sarthe and Old Mulsanne circuits, but also the Bugatti Circuit which is steeped very much in racing history.
There is also a rather nice Audi Vidoc that you can watch below.
via Forza Motorsport - Audi ViDoc