We'll have to wait and see how much PS3 will sell at $249 and at $199 to be able to give a sensible prediction, at the very least we'll have to wait and see how much it will sell during the year after the drop to $199. If it will sell more than 60M in less than 6 years from its launch, 100M will be possible (with at least a cut down to $149 or less for its last 2-4 years).
But there are still too many "ifs", we can't really answer now.