The Sony PS2 has sold over 140 million units over the nine years on the market. For Sony's Kaz Hirai it is clear that the Sony PS3 needs to beat that number. At the E3 2008 he set the overall sales goal to 150 million units for the PS3.

The Sony PS3 sales since its launch are around 13 million units, so there is still a very long path ahead for Sony to reach 150 million. Of course Sony bets to see the same adoption curve they have seen on the PS2 over the almost 10 year life cycle.

A more radical price-cut instead of a larger hard-drive would in my opinion dramatically speed up sales for the PS3.
More details on the Financial Times.