I missed this yesterday as I was pulled away from my PC for some time:
Kinectless Xbox: Why announce it now?
I think the answer is simpler than most are making it out to be. They don't want to dumb down their E3 with essentially hardware revisions, but at the same time, they couldn't get the new SKU out the door immediately. With the delay from having to put together the new SKU, produce the new units, and then get them out the door to retailers . . . and then have retailers do their thing, it just couldn't be an immediate turn around.
That, and any media attention is good attention. Spread that shit out. How many articles were written on "ZOMG, is this good news or bad news for Xbox One?!". And with it being announced *now*, it'll have died down just in time for E3's big reveals.
I don't think Microsoft cares about the numbers terribly much. I mean, they want to sell a lot of units as their end goal, but using it as a "this is why!" excuse for investors is silly. The investors aren't going to buy that. The investors know why it's not selling.