http://ca.ign.com/articles/2013/07/16/forza-motorsport-5-requires-one-time-internet-connection
“[But] that is required content to play the game. We basically have designed the game to work with all that content no matter how late is coming in, in order to make the biggest game possible.”
In other words, because games have to be submitted to Microsoft testing, certified, and then pressed onto discs and shipped, Forza 5 has to be done much, much sooner than November. By requiring part of the game as a download on launch day, it gives Turn 10 extra time to finish everything. And so what you get on the disc you buy at the store won’t be the entire game. You’ll need to download the rest of it from Xbox Live (which should be possible to occur as you play, Greenawalt clarified).
En el disco que compréis de Forza 5 el juego estará incompleto. Será obligatorio hacer mínimo una actualización del juego para poder hacerlo funcionar. En la actualización se descargará el cacho de juego que falta.