Before seeing the trailer, I made the following predictions. These predictions aren't very specific, and they aren't difficult to make.

1. The movie would feature a "Through the Looking Glass" theme

2. Supporting that theme would be the concept of traveling through mirrors to get into the Matrix

These aren't actually predictions; they're just recognizing the theme of the first trilogy. The first movie started with the famous line "Follow the White Rabbit" displayed on a computer screen. Neo starts his whole journey "down the rabbit role" by literally following a girl with a white rabbit tattoo. Since "Alice in Wonderland" was followed by "Through the Looking Glass", it had to be that the 4th movie would feature at least a passing reference to Lewis Carroll's sequel, and likely that the theme of a Mirror would play a larger role.

The Matrix series draws heavily on its metaphor of the world as a computer. Regarding the "Through the Looking Glass" theme, keep in mind that the term "mirror" means something else to a programmer. The director will have known this and used it as inspiration.

Here is the definition from Tech Terms (emphasis mine): "In computing, a mirror is a server that provides an exact copy of data from another server. This may be one or more files, a database, a website, or an entire server."

Let's add something else to that last sentence: "This may be one or more files, a database, a website, or the entire Matrix". The new movie might have something to do with a backup copy of the original Matrix.

I thought a mirror was white, since white is a reflection of all color on the light spectrum, and mirrors reflect all light. However, it turns out mirrors are actually slightly green, since mirrors reflect green light stronger than other colors on the spectrum. That's a key thing to be aware of.

I recommend looking out for green-tinted scenes in the upcoming movie. But there's even a crazier thing going on here, possibly.

The colors in the new trailer are noticeably brighter than the original trilogy. This might seem like a modernization at first glance, until you remember that the original trilogy had a slightly green tint to it, while in the Matrix.

That's funny. The original Matrix had a slightly green tint to it... sort of like how a real-world mirror has a slightly green tint to it... sort of like saying the original Matrix movies may have taken place in a mirrored copy of the Matrix, all along. Maybe now we are finally seeing the "real" Matrix, and there is another "real" real world?

Good writers and directors consider every detail that goes into their movies. They pick their themes and use them to guide their visuals. They leave hints about plot twists scattered around. If you know the themes and the capabilities of the director, you can make decent "predictions" about a movie's plot or various elements that will be a part of it.

Things to look out for are color themes, words, phrases, cultural references, specific actor movements that seem out of character, etc.