I think the "temp" price drop will be permanent. it will be 350, until the first hardware revision then it will drop to $329.00
The same with Sony, won't see a price drop until there is a hardware revision for them too. Then I think they will drop to 379-359. Sony will not try to achieve parity in price. I think they are fine with having the slightly higher priced console. It is the strongest console with the highest appeal this gen so far, If that changes in a few years, who knows.
But I think MS knew Sony could not afford to do a price drop this year during the Holiday sales bonanza.