Only if they want to continually lose money. At some point they will actually want to profit on the PS3, and I'm sure they have a point where they will be happy enough with their stake in the market share, their share of attention from developers, and general place in the war to stop taking losses on their system and start profiting from it. What good is having the majority of the market share if at the end of the gen your bottom line is tens of billions in the red?
At some point they are going to say "good enough" and start making money, so I think that it will be a good while before they get to 300 and maybe at the end of the gen when the new systems are coming out it will get down to 200.
You can find me on facebook as Markus Van Rijn, if you friend me just mention you're from VGchartz and who you are here.
