There might have been an extra-bit of info posted afterwards that clarifies things. But nothing in the original article mentioned
Kinect specifically having two players max in a game.
The only mention about the processing limit was this: "and the computer will see all of them and can even recognize them as human shapes. But it can only run calculations on two people at a time, just because the processing power required to track all of the body's locations and movements is so great."
In the first place, it does not specify what "the computer" is. We know that with Kinect specifically (which may or may not apply to 'raw tech' the company is referring to), there have been some modifications since its announcement. Such as the removal of the on-board processor(s) and relying more on the 360's own processing power. Microsoft has stated before the hardware could change before it is shipped. So that could very well alter things.
Beyond that, it is unclear how much of the software side of things factors into this. Since Natal was first revealed, Microsoft (and affiliates) have gone on about how the amazing part of tech is the software aspect such as
here or
here. Of course, it could be the limit is on a lower level than that.
No time frame was given on the two-player processing limit either. Some games might be able to allow four-players depending on the type of game and how information is stored.
Ultimately, I don't think there is any definite statement about Kinect in that article. At the same time, there hasn't been any game shown so far with more than two people playing simultaneously. Though the Kinect Adventure descriptions I've read varies between two and four player support (which may or may not be simultaneous play). I would wait till Microsoft actually comments on it.