Because announcing it one month before gives them an excuse for the very low sales they could not avoid anyway ;)

They are tomorrow

April and May NPD. Simple as that. The excuse about just showing games at E3 is bullshit. This announcement could literally take 2 minutes at the conference.

And will no doubt at all still be in the conference, for 5-10 mins.

I think its a more imediate reason. They filled retailers with the kinect version. Retailers probably dont want anymore. The only way not to stop production was to come up with a new model that retailers want to buy.
Early adopters arent the only ones burned by this, as retailers are also left with quite a bit of inventory from the kinect pack. I imagine retailer price cuts on them will return in the furure.

I think they caused a lot more harm than good by announcing the price cut right now than waiting till e3. Sales are probably going to go down until the new sku comes out, as others have said. I wonder how the sales are going to be that week. And to answer the question, maybe they just wanted to get it over and done with incase it caused some negativity. 

Those that think it is because of NPD numbers, should opt out of donating organs

Phil specifically said that they wanted to leave time for more game anouncements.

Can't imagine what they could possibly have to show that would be a bigger megaton than this, but my HYPE level just went up by a ton!!!

shit is real and very very stinky, have to change fast, cant wait till E3---

Its because of World Wide sales plain and simple.