The idea isn't that they will replace discs with digital distribution entirely, the rumor says they will have some sort of solid state memory for games. (gimmegimmegames.com)
Solid - state memory chips — as opposed to hard drives with moving parts — come in two forms. (newscientist.com)
However, compared to the PC, only a limited number of game save slots is available due to the size restriction of the solid - state memory supported by the device. (adventureclassicgaming.com)