Last month, Sony confirmed rumors that were running rampant about a discontinuation of the 60GB PS3 model. The lower cost model, they claim, wasn't selling as expected. While I would wager a guess that no PS3 was selling as expected, they still decided it would be best to not offer the 60GB unit any longer.
Now, stock of existing PS3 units has dwindled to the point where Sony's warehouses have run out, meaning the world's supply of these units is now solely with the retailers. With a price drop on the way, it is likely that it will come as soon as retailers report that they have exhausted their own supplies and there is little reason to delay it any longer.