There will likely be one more proper PS2 price cut.... any cuts after that will just be stock clearance after they stop making them.... The PS2 won't just keep getting little price cuts until it is $10 because cutting manufacturing costs is not a linear process, so there really won't be any way to make the PS2 cheaper now than they have been making it the past coupld of years.
The GameCubes last real price-cut was to $99 I think, which will likely be what the PS2 cuts to, perhaps this Christmas as a last hurrah.
A PS3 price cut depends on how dire it's situation gets.... I fell they will hold out till at least Christmas, so the price cuts may be at about the same time, but Sony may need to hold out longer.