If you are looking to get a 2011 below MSRP and you KNOW that you want a 2011 without needing a test drive (just test drive a 2010 and then look at an STi) then you should consider pre-ordering now instead of waiting until they hit dealerships.
I worked with several dealerships in getting prices on a 2011 and the basic understanding I have is that when it's a pre-order, they are able to work the books a little harder to get you a better deal. When you think about it, it makes sense. A pre-ordered car is just about no work for the dealership. They place the order, call you when it's in and then cash the check. For a car to stay on the lot they have to pay fees every month, they have to keep it clean, take it on test drives and deal with the potential that it might not sell at all and depreciate.
I wrote up a thread detailing my experiences here:
My journey to purchasing a 2011 WRX
If you don't have the choice to do this and you need to wait, then I would say that you still have a very good shot to walk out of a dealership paying somewhere between MSRP and invoice price for the car. You may need to comparison shop at several dealers to find one that will play ball with you, but the discount is worth the effort.
Good luck and happy hunting!