Other way around actually. Sony forced MS's hand by dropping early. Every single year.
http://en.wikipedia.org/wiki/Xbox
http://en.wikipedia.org/wiki/PlayStation_2
In the UK they dropped $100 after only 10 months, when the XBOX wasn't even on the market.
That's a completely different situation. PS2 was already out and doing VERY well when Xbox launched. This time it's the other way round.
If anything, i seriously expect Sony to do what MS did with the Xbox, lowering the price very soon. But MS won't, unless they see that PS3 is really slowing them down, which it won't for a long time due to shortages. And to be honest i don't think Sony will either, unless they really feel threatened. Heck they had already lowered the 20GB PS3 price from what it was supposed to be, even before it launched!