I was just watching through the trailer again, and noticed something interesting about the combat, especially in light of what Kitase and Co. said in the interviews.
When Cloud and Barret are doing regular attacks, the "attack" command in the menu is blue, and blinking - in fact the entire command menu is blue and pulsing.
However, when doing special attacks and the ATB bar is full red, everything is grayed out.
Also, the part where Barret is doing his special, and Cloud's ATB is completely drained, Cloud is standing entirely inactive next to Barret until Barret fires his charged attack, and only then does Cloud start running towards the enemies.
This might suggest some kind of cool-down, or "end of turn" mechanic.
Up until this point, people have just guessed that the ATB gauge was just some sort of combo-guage - but it might actually be the case that gauge doubles as a limit on the actions you can take "in 1 turn" so to speak.
I.E attacking builds the gauge, allows you to top it off with a special, and then puts the player on the defensive until it goes back down (which would be the ideal time to swap to another character that's no currently on cool-down).
Even if this turns out to be wrong though - at the very least it probably suggests that the moves/actions of characters cannot be spammed into one another the way that you can usually do in action games.
Taken together with the how the devs envision the system as being "Dissidia > KH > FFVIIR", the inclusion of the wait system in FFXV (which shows that SE devs are conscious of how action battle systems impact strategical play involving the use of a party) I'm actually less and less concerned about this turning into an action fest.
I think we're looking at something like a mix of Dissidia's RPG battle system setting in turns of how commands are carried out and KH in terms of mobility and how enemies are encountered -
Selecting commands and targets, whilst the characters largely attack automatically - and then using some sort of cool-down to create breaks in the game-play that allows the player to focus on browsing through spells, changing targets, which character to control etc.
Another hint suggesting such a system, if combined with everything else, is that at the first point where the player is controlling Barret, Barret is moving towards the screen firing at an enemy that isn't even on screen.
That's pretty unusually for action systems with a functional targeting systems because usually targeting an enemy (which you probably have to do to hit an enemy with someone like Barret to begin with) usually auto-focused the camera over the shoulder of the character directly at the enemy.
If however, characters move pretty automatically as is the case in Dissidia's RPG setting, it wouldn't matter. You'd be free to move the camera around in whatever way you please whilst leaving the character to its own machine (at least for the duration of one attack-loop, until the ATB bar resets).
In the context of having a party - that makes even more sense, because, as you can see in the trailer, you can keep track of Cloud's movements in the background, which is vital if you're aspiring to retain full control over your party at all times.
Of course that part might simply be a fluke caused by some sort of soft-targeting system, and the player not attending to the camera, but combined with everything else we know, I think there is a chance that it's more deliberate than that.
Anyway, so I guess my predictions for the battle system summarized are as follows :
1.) You have partial control over movement in battle, but the characters will move around automatically even if you don't push the movement stick, which allows you to constantly survey the battle-field using the right analogue to keep track of what's going on even as your party members carry out their commands.
2.) You'll select commands from the menu, which the characters will then carry out automatically for the duration of one ATB meter, or round.
Selecting attack will probably end with a special attack and the game will probably allow you to customize and set up combos.
Selecting magic, items, or summons rather than how the attack fills the ATB meter by connected hits, will fill the ATB meter in one go, and cannot be used again until its empty again.
The strategy of the game then is found in rapidly switching between characters to give them orders as their ATB is on zero, and using the time when they're either working their attacks up to their special (and using the special), or in the period after casting magic or items to consider your options - your next round so to speak.
So guys, write it down in stone. If I'm right when it comes out, I'll be going, "CALLED IT!!11!1!11!1111!!!!!"