Well it's no L.A. Noire, so there definitely won't be 3 discs.
I'm sure it will all be on a single disc, just like GTA IV.
Proud owner of the following threads:
EA Sports UFC - What Are You Expecting from EA?Thread
Dishonored - GOTY Edition Coming
Xbox One - *Last* Chance for Day One Editions Via Amazon
That last one means a lot to me, so please rate it 5 stars.