I know all are rumors, but I don't think that the "negativity" is a good sign for a company. MS is getting a LOT of negativity, not only for next gen consoles.
They are not ready to talk about their next-gen platform, simple as that. If the rumours are true regards the hardware, the only 'comeback' is to show the whole platform as an incredible experience. Show Kinect and the new interface and the whole experience in a big, impactful splash. What else are they supposed to do? Tweet "our hardware is great" or worse, "yes, the hardware rumours are true, but its actually quite a good, well balanced system"? And if it's not true, all these rumours are immaterial because when MS do unveil, people will care about what the platform is, not what they thought it was. No-one's going to avoid buying an awesome machine because they believed it wasn't much cop before it was unveiled.*
There is absolutely nothing to be gained by revealing before you're ready, showing glitchy software, incomplete interfaces, games you hope will be finished and impressive. Whatever hype exists for Sony's console hasn't been because Sony have been generating it, prior to 20/2/2013. It's just been gossip. Neither Sony not MS were ready to reveal. Sony feel they having something worth showing at this point; MS will wait until they have something they feel will engage gamers.
*And that's using the common gamer vernacular. The hardware, even if rumours are 100% accurate, could still be a compelling experience at excellent value and the platform a majority of console gamers want.
EDIT: What if Sony start to accept pre-orders before Durango unveiling?
Just stop a moment and think that through. Preorders aren't binding and you can cancel. When Ms are ready, they unveil their machine and blow Sony away, and all those preorders are retracted. If MS can't do that, can't compete with Sony and win customers over, then it really doesn't matter when they start talking. Ergo, the only sane, logical thing to do is bide your time and prepare your message. It really doesn't matter at all what goes before your info. Only a few numpties are going to go crazy over unreleased boxes and runoured specs. The rest of the world makes sure they know what they are getting and buy a moderately informed choice, or buy brands blindly where it really doesn't matter.