^^
One thing's for sure: if Sony needs to cut price, it will have to plan it very carefully to make sure a possible MS reaction has the smallest possible effect, for example delaying it so much that MS can't counter it in time to make it fully effective during next Xmas season. Or doing it in two phases so that if MS wants to counter both by significant amounts, XB360 Arcade would generate horrible losses.
A third way always implies delaying the cut as much as possible: this way, thanks to lower components cost, the cut could be bigger than what MS expects, so that if a reaction was already planned, it should be rethinked and tweaked in a short time.