Trago has an epic computer?
So you'll be using MegaMawile in XY, then, Trago? Welcome to the master race.
Wouldn't recommend it 'less you've plenty'a SD cards for exclusive 3DS usage. It's gonna be a lot of memory, even for a 3DS game. It's even larger than FE: Awakening, and literally ties with MH3DS at 1.7 Gigs.
Assumin' that source ain't bogus. Wouldn't be surprised if XY is that big though. The soundtrack is retardedly huge, there's a ridiculous amount'a 3D models... and who knows what else in the game might require a shitton of space. The overworld is definitely a decently sized chunk'a memory, what with huge (3D) areas like Lumiose City.