They won't drop to $300 if they want to make a profit at some point. That would be economic suicide. And 360 and Wii would drop their prices as well, making the cut much less useful. Sony is doomed to abysmal American sales, and Wii will keep its 70+% marketshare in Japan. The only place where PS3 will do well is Europe, and it is still being dominated by the Wii. Do you honestly think that the Wii will suddenly stop selling when PS3 is cheaper? Nintendo can't keep up with demand right now, and I don't think Sony will ever get to that point.
Plus, sales of Devil May Cry 4 will be better on 360 than PS3, especially in America, the territory with the strongest sales for the Devil May Cry series. Plus, I think sales will be between 1 and 3, but split 60/40 across the platforms, which means around 1 mil for PS3 version, and 1.5 mil for 360 version.