Maybe I´m alone on this one but I think even a pricedrop wouldn´t have changed this months´ NPD result by much. Imo Microsoft needed to win this NPD really badly so even if Sony dropped the PS4´s price to 349$ MS would´ve undercut them by another 50$.
Cleary, they would not have had any assurance they just don't feed a price war they can't win. It could even what MS hoped, at least what they were ready for. Anyway, Sony still has a worldwide advantage, an advance even in america, and can enjoy profit, I don't see any good reason for them to rush. It's not even a bad thing MS spend their money on price drops rather than on exclusive games and new studios.