This trailer ^ has certainly become my favorite newcomer trailer thus far.
Some Thoughts:
(Keep in mind that I'm writing my thoughts as I progress through the trailer, so things written earlier may be disproven things written later.)
I see some of you thinking that at 1:17ish Robin switches Tomes while rolliing from Wind to Fire. Well, I've been watching it repeatedly and he doesn't actually change tomes, slow the footage down when Robin is doing his D-Tilt on Captain Falcon and you can see that the Tome's binding is red, signifying it is a Fire Tome. The scene just before that where the camera flies over idle Robin (holding a Wind tome) is a completely different scene.
Neutral B is a Tome Charge move, given that Robin cycles through tomes I feel like each element may have different charge characteristics. For example, Robin's usage of Arc Fire at 1:36 could potentially be his fire tome neutral charge. You also see this Arc Fire animation again at 2:02 and 2:12, since Robin can perform this move in the air and seems to "pause" before releasing the fireball at 2:02, I feel that this move is the Fire Tome charge variation of Robin's Neutral B. This is further supported by the fact that if you closely observe the size of the Fireball that forms over Robin's head during the animation of Arcfire, you will notice that it is smaller at 2:02 than it is at 1:36, so the size changes with charge time, as far as I can tell. Elwind, at 1:36 seems like it is more than likely a special move considering the vertical distance Robin covers when using it, if it were a Dair it would make his recovery broken to say the least, it also has two different animations with different trajectories, but its complete characteristics have yet to be seen.
At 1:22 you can see Robin's grab animation on Diddy Kong, where he reaches out with the Bronze Sword in hand. This makes me think that the grab attack he performs with Nosferatu on Palutena at 1:38 is a command grab. Also, if you slow down the footage and watch Robin as he executes it, this move seems to be a Down B as he seems to be going into a crouch (and then stands back upright) right before the grab animation initiates here. Also, it seems that the Damage done by Nosferatu comes in short bursts, as you can see that the Darkness pulses for a second or two and then fades, and then after a pause, pulses again. Something I noted though was at the beginning of the move there was "gold flash" but the move doesn't seem to be a Down Smash as it seems you see that (or maybe the F-Smash) at 1:47, which Robin performs with the Levin Sword, I think the attack at 1:47 may be a down smash considering that the lightning extends to both sides of Robin, but it has yet to be seen what this move will look like without the Levin Sword (Robin was holding a thunder tome, so perhaps that is what caused the electricity on the ground, although I doubt it).
You can see variations of Robin's neutral combo string at 1:17 and 1:40, with a Fire tome and Wind tome, respectively. Fire tome seems to be the typical 3 hit combo while Wind has an infinite end similar to Fox's (the fact that it is a neutral combo infinite is supported by the "finisher" that you can see for the combo in the Wind Tome clip).
It seems that Robin will have to switch tomes on a regular basis, whether she auto drops them (akin to how they "break" after so many uses in the FE games) or the switch is player-controlled has yet to be seen (perhaps the tome stops functioning after a time and does have to be manually switched, signifying that it is "broken"). I hypothesize that maybe this switch is done with an execution of Neutral B (when the tome runs out), since it is the "charge" move of Robin's specials. Additionally, I feel like it is possible that Robin is "locked in" to a certain tome for a bit until it breaks, I'm assuming it will gradually wear down as specials are used and such, so players can spam special attacks in order to work to switch to a different tome. This is all just speculation of course.
A note, during Robin's final smash (2:33) it seems he first attacks with a Thunder Tome and then attacks with a Fire tome before reverting to Thunder, you can only the binding of a Thunder Tome, but I feel like he does switch tomes considering the different explosion animations (lightning, then fire).
NOTE:
At 2:40, when Female Robin is shown, the fight clip opens with her using a Fire Tome. BUT, at 2:42, you see her stand upright, and a light quickly flashes where she is holding a tome. You can then see her attacking with a Thunder Tome. As such, I strongly feel now that Robin has a specific special move allocated to switching tomes (I feel it is her D-B, with her Nosferatu command grab I mentioned earlier being a S-B variant).
On the topic of weapons "breaking" like in FE, some of you have noticed that Robin was seen with both a Levin Sword and a Bronze Sword. Since weapons "break" in FE, and Robin is shown using both swords at different times, I get the feeling that Robin may start the match with her Levin Sword, and that the Sword breaks after a certain number of attacks. After this, she switches to fighting with a Bronze Sword (a wise choice considering that Bronze Swords last much longer than the Levin Sword) at the (probable) cost of losing some attack power (since the Bronze Sword is weaker than the Levin Sword). As such, I hypothesize that Robin will start each of her stocks with the Levin Sword, and then eventually lose it as it "breaks" while she is fighting. When she is KOed, the Levin Sword will return and the cycle repeats itself.
Again these are just my thoughts, I cannot even begin to think of what her special move variations will be, considering the vast options she seems to have just in her default moveset.
I remind everyone that all of this is just speculation at this point, but I hope you enjoy reading and I look forward to your thoughts.
Thank you for reading.