David Reeves, president of Sony Computer Entertainment Europe (SCEE), has made it known that his company believe the PlayStation 3 will sell more than its predecessor.
PS2 total is around 127m. PS3 is around 13m. The PS2 has been pretty much beating the PS3 in sales except for the last three months. PS2 sales have dipped quite a bit in the last few months, while PS3 sales have dropped by less in the same period.
It all depends on how much the PS3 picks up, and whether there is a point in time when PS2 to PS3 upgrades start to happen (I would think price is the main issue right now).