Art Evolution: A given, since this game is taking advantage of the new consoles. The art style may change as development progresses, but the E3 2013 trailer maintains the original anime-influenced style (that is, it's closer to the rest of the series' in-engine rendering as opposed to resembling the photo-realistic full motion videos) but with better shading, more detail, and brighter colors. That said, the tech demo's graphics indicate a small shift from the previous games' anime-styled character designs to a more stylized design that shows some clearer Disney influences.
Art Shift: According to Nomura, each world uses its own shaders. The new graphics make the game look more like how it did in previous games during the CGI cutscenes.
Avengers Assemble: On two fronts, if not three. We have Sora, Donald, and Goofy fighting together for the first time since Kingdom Hearts II, their quest to gather the PrincessesofHeart, and Riku teaming up with King Mickey to search for the remaining Keybladers of the Light. Numerous details from previous games all but state that Kairi will join them in some Keyblade-wielding capacity, as will Lea, in all probability.
Back For The Saga Finale: After spending about a decade on the sidelines, Donald and Goofy will be a part of the main cast once again. The Rock Titan will also return, last seen in a cameo in II.
Bag of Spilling: As with every game in the series that Sora stars in, he will have his stats reduced to zero once again. This time, it will most likely be due to having his heart shattered in Dream Drop Distance and needing time to recover from that.
Never Trust a Trailer: The "gameplay" in the E3 2013 trailer is actually a target render—i.e. pre-rendered footage of what the game is intended to look like. The shader technology was not complete enough to show off for actual gameplay.
Scenery Porn: The peeks at the graphics we've gotten so far are gorgeous.
Wham Line: "On that land shall Darkness prevail and Light expire. But you knew that, didn't you?"
Wham Shot: During the E3 2013 announcement trailer, many fans assumed it was another trailer for 1.5 HD Remix based on the opening montage of the previous games in the series. Then we see Eraqus' Keyblade, and then Sora in PS4 graphics.