I'd like to add my own spin on the "is it always 1999 in the Matrix?" debate. Personally, I think the "always 1999" idea is an interesting interpretation, but it does not present a complete picture. My interpretation? In terms of the films, it is always the year it is when one is watching the films, because the Matrix is the everyday world as we, the audience, experience it. The Matrix is not some hypothetical alternate reality that may exist in the distant future. The Matrix is now.
Let's look at the philosopher commentary on the Ultimate Matrix Collection. Ken Wilber and Cornel West propose that the "green" world of the Matrix represents the Mind, the "blue" world of Zion and its hovercrafts represents the Body, and the "gold" world of the Machines represents the Spirit. I generally agree with this assertion, but I'd like to make a small addendum. These things are not merely representative of Body, Mind, and Spirit, they actually are Body, Mind, and Spirit. It isn't the case that when we see blue, we're dealing with Body, when we see green, we're dealing with Mind, and when we see gold we're dealing with Spirit. In actuality, we're dealing with all of them all the time.
The complex system of the Matrix is the world of Mind. It does not only exist when we are plugged in, it exists, and exerts its influence, whenever we are thinking beings able to imagine hypothetical scenarios of past and future. In short, if we are perceiving a linear flow of time, we're in the Matrix. Linear time and narrative is essential to the human being's intellectual conception of his or her self, so anywhere there is a narrative (and thus, some conception of time), we are in the Mind, and thus we are in the Matrix.
The tactile world of skin, metal, earth, and stone we awake to after exiting a place where we are trapped in the Matrix (and thus the Mind), is indeed the Body. But The Desert of the Real does not exclusively represent the Body. This would imply that only the Body is truly real. Actually, reality consists of Body, Mind, and Spirit. So the real awakening that occurs upon being unplugged from the Matrix is an awakening into being able to perceive Body, Mind, and Spirit simultaneously, rather than looking at all reality through the purely representative lens of the mind.
Once we are awakened, we can see Spirit, as well, but because there is disharmony in the human condition, because the Matrix (which we are always a part of as human beings whether we are plugged in or not) is world of suffering, we see Spirit, our own experience of the totality of being, as a cruel attacker, a monster, a demon. We are trapped in Hell only because we imagine that Spirit is malevolent. It is our imagination, the world of Mind, that creates the relationship between Man and Machine. Essentially, Mind is responsible for the conditions of the relationship between Body and Spirit. As Morpheus says, "the Mind makes it real." And thus the Matrix, the individual and collective world of Mind common to all human beings, is responsible for how we relate to the Machines, our greater Spirit, our conscious, our higher being, our totality, our ultimate. Because we are at war in our minds, we are at war with Spirit.
The key to all of this is that, although we see Body, Mind, and Spirit presented in the Matrix films, we see it all, ultimately, through the lens of Mind, because the only way to watch a film is through that lens. Watching a film involves the conceptualization of time and narrative, and thus when we are watching "The Matrix," we are in the Matrix. So for us, as viewers, the Matrix exists at whatever year we watch the film in, if you want to designate a year to its architecture. Now, literally, the year of the Matrix is stated in the first film is 1999, and the next two films take place six months later, so still, probably 1999, but my point is that the Matrix is not a system that can only contain the year 1999, because the Matrix contains the entirety of time itself. When people are unplugged from the Matrix, they awaken into the timeless world of the Real, but the grasping mind (still very much trapped in the Matrix) has to assign time and narrative to this experience, and thus, the mind experiences the Real as existing in the very distant future of the world they knew. But it is no more 2199 in the Real than it is 1999 in the Matrix. The human's entire perception of time is manipulated by the Machines, who see manipulation as the only modicum of interaction with humans because this is the only modicum that the humans have presented via the world of the Mind, the Matrix.
In short, while the events of all three films occur in 1999, this does not mean the events of the Matrix are limited to 1999. Things can change, narratives will occur, because that is intrinsic to the condition of existing in time. The Mind alone perceives time as a relevant factor. The Body cannot perceive it, at least not in any conceptual way, and the Spirit is so far beyond it that it no longer matters. The Body perceives only the present, the Mind perceives a conceptual past and future, a linear flow of time, and the Spirit perceives a timeless Now that transcends and includes all sensation of present and conception of past and future. The Matrix includes all times because the Matrix is the Mind, and thus the Matrix is time itself. However, from the perspective of the Real, which includes Body, Mind, and Spirit, this time does not have to unfold in a linear fashion. It will merely appear linear from the perspective of the Matrix.
How does all this relate to Matrix Online? Well, for the majority of our time here, we seem to have been stuck in 1999, trapped in one specific instance of the Matrix. In certain glorious moments, though, I think we've found ourselves awakened into the world of the Real, transcending and including all time and space, which ultimately exist only as concepts. I think the Matrix still has stories to tell that go far beyond 1999. The only question is, are you ready to see how deep the rabbit hole goes?