Ok, so I looked at the Trailer, and other peoples theories (I'll show the video I found the information from at the end of this chapter), and this is what I've figured out:
There is 7 dark figure's shown in the new side order trailer, and some strange creature below the tower the dark figures are standing on. I have a clue on who at least one of these figure's is.
This figure in the middle is similar to agent 4, they have the same tentacle haircut, hero headset, everything.
It looks like 4 will have a appearance in side order, and might be a major Villain in the DLC.
Some things I asked myself when I saw this was, Why is she here? Is there other agents here to?
In the new DLC trailer, we saw the new Agent 3, in the same place she was in the train in the start of Splatoon 3 but this time, she was asleep. In the new trailer it shows what looks like her being transferred into the world of order. Some people think this means its just a dream, but I, and others think that it means that someone or something is altering the timeline of Splatoon, and taking the agents, and others into this world.
This means that not only will we potentially fight agent 4, but we might also see 3, the Captain, the squid sisters, maybe even deepcut, Cap'n Cuttlefish, and DJ Octavio. But that's a maybe.
There is one thing I think is likely, and that is in some way we will see multiple of the agents within this world of order, because if agent 4 is here too, and 3 is getting transferred in somehow, then maybe there are others that got into this world as well.
I am not sure about the strange creature I saw below the 7 dark figures, but that's something we'll figure out later.
I can't be certain about this, but looking at the trailer's, it seems likely this might be the case.
Anyway, that's all I figured out for now! See you all next time!
Here's the video with the theory (It may also explain it better as well!)