I think the fact that they are wearing their old clothes doesn't mean anything in terms of the timeline
Judging from the pics it just seems to me that those developers are a lazy bunch and just put in already existing objects for a quick demonstration of the game (you know traverse town, twilight thorn, old sora + riku) .. there was nothing new in the pics yet
As for the trailer, no one but a selected group of people saw it until now, so these pics could just be beta pics because the new outfits weren't done yet or for whatever reason
Although it could also be possible, looking at the trailers description, that there will be a lot of "Sora Clones" (from kh wiki: "Riku is looking up into the sky to see several unconscious Soras raining down from above")
Maybe these were forged using the data collected from the sleeping Sora.. dunno
Edit:
I just came up with this check this out:
Maybe all of KH3D is happening before the first keyblade war, and riku + sora get reborn everytime in order to save the world
that would be so typical for a nomura mindfcuk
