You seem to think that only Sony knows what they are going to do come this holiday, but for some reason assume Microsoft is only making counter moves with comments that if they luck out and Sony only drops by $50. Both companies have lots of options and both companies are calling their own shots and have contingency plans based on what the other company does.
One of the basic laws of economics is if you are unable to afford to lower the price to increase sales you add something that adds real value that doesn't raise your costs significantly. Both companies could do better with some better bundles. I'd like to see a Killzone/MGS4 bundle (yes both games). I would also like to see a Gears of War / Halo Wars bundle.
I wonder which company will be smart enough to have the Modern warfare 1 and 2 bundle.