I'm not sure why people are comparing this to a 3DS/Vita situation, or if they're being serious about that. The PSP was never a blip on the radar in the west and neither was the Vita, while the 3DS was following the DS. Sony's draw in the handheld market over here isn't even a fraction of what it can generate in the home console market.
On topic, I don't see this hurting Microsoft. They are masters at hype. Remember when Project Natal was going to change the face of gaming? Remember Milo and that video where we never had to leave the house because Kinect did everything for us? And, because it's Microsoft, the media interest is going to be through the roof.
No, regardless of which console is announced first, it won't make much difference ultimately.
With the Wii U, however, I'm not so sure. People on the fence about buying one, those that don't follow the gaming industry closely, might decide to wait if the PS4 is announced this early. It could hurt some of the business Nintendo was hoping to do before the rest of the next gen caught up. Remember that the average consumer doesn't think of systems in terms of "generations", just by what is out or announced when they're thinking about buying.
Not that I think the effect will be extreme. Those who want to play Nintendo games will buy a Wii U.
