It's generally not wise to start a price war since in this case, Sony is likely to react like in Japan. If they want to hurt Sony (while they are slower/less likely to react), then they should drop earlier. OTOH, they also have to figure out how to make money (which is more important, really.... unless they want to make it personal).
That's why I think they are less likely to drop until end 2007 where they have ample time to validate/work out their profitability. My guess is still: No drop unless MS has figured out its profitability, or unless Sony starts it first. I can be wrong though
EDIT:
Sure hardcore gamers, such as ppl writting here for ex, will buy the console that carries the titles they want. But they are the minority, the casual gamer, the parents of very casual gamers (kids) will definitely look at the price.
People here and on other boards downplay price, which is understandable considering what our interests are, but in the end price is king.
Also, consider that a lot of people (me!) don't care too much about the exclusives and the titles they want are available on both platforms!
I agree that MS may use a price drop in march to bury the PS3...
Sure, but if Apple can do it with expensive iPods... don't you think MS will try similar tactics ? An Xbox 360 is not much more than the high end iPod (How much is it going for these days anyway ?). They went aggressive by even pre-announcing their video service to jump on Apple and Sony. MS also wants to rev share Zune sales with music companies.
For the value and for the rev sharing and flexibility in execution, they may want to have more margin to play with (for now). They can always dictate when to drop price since they are the price leader now. So why rush ?
EDIT 2:
I just want to add that...
Even though MS may not drop the official/list price of Xbox 360, they can still introduce incentives such as promotions, discounts, coupons, subsidies, rebates and bundles to the consumers or partners. This means that it may be possible for someone to buy an Xbox 360 at lower (final) price.
e.g., Comcast and MS may partner and bring USD 99 Xbox 360 to new Comcast customers who subscribe for 2-3 years.
I have not seen SCEA do this kind of co-marketing (yet ?).