The good thing about new generations is that we don't necessarily need established franchises. We are open to new ideas. Look at the Xbox 360. People never heard of Gears of War, Dead Rising, Saints Row, or Lost Planet but, because these games were showcasing graphics and features that really got gamers excited, the games sold really well and sold a lot of hardware, too.
All Sony needs is a game that gets people excited about the potential of the new hardware and they'll be fine. Two or three breakout titles like Uncharted (which was also an unknown entity when the PS3 launched) and we'll have another hit console on our hands.
Uncharted, Heavenly Sword, Resistance, Motor Storm--all were unknown titles at the start of the PS3's life that managed to garner hype for the console. Some of them went on to become big franchises and others didn't but, at a console's launch, people are hungry and those types of games are quite satisfying.
