Yes and no. I think there's a good chance that Nintendo will help elongate the 360/PS3's lifespan. With a Wii2 in three or four years, porting over to the PS3/360 might be a low-cost incentive to tack on a little profit to a title.
But it will have nothing to do with Sony. If Nintendo releases a more powerful system that can't easily do ports or if they don't release a system at all, expect both the 360 and PS3 to die quick deaths once the PS4 and NextBox are released.
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