Hmm. I have constructed a theory based on this picture of the day.
First off, If I recall correctly the official name for aerials is aerial smashes; therefor his midair attacks use Levin Sword if it's available. So does his forward smash. I suspect it will not be ALL of his aerials though, just some. Same with his smashes.
Now, I'm fairly certain we see a forward tilt and down tilt in the video; the down tilt is the first attack Robin uses on Captain Falcon, and forward tilt is the move Robin uses when confronted with Marth & Ike near the end. It appears that in both cases, it is a simple sword swipe with the bronze sword. I suspect part of his tactician design is that Sakurai wanted to make every single move have an important use in strategy, so simple, potentially weak but also quick attacks, are going to be Robin's bread and butter for early game damage, before he starts slinging big spells or the like. While he has the Levin sword, these attacks may change but I think it's more likely that they remain the same but get powered up in terms of damage and range.
I think the prevailing theory on his specials (Neutral = Thunder, Side = Fire, Down = Dark, and Up = Wind) is very likely, and I also suspect that the last special move used will alter his moveset. At very least it will alter his jab, as I think we see two variants on it, the fire jab (the one two three combo he pulls on Captain Falcon) and the wind jab (the massive multihit combo on kirby). This leads to another level of strategy in his gameplay; you may want a certain tome colour equipped for certain attacks, but if you do not have that tomb equipped at the time, you need to decide if using a tome's charge is worth getting that, especially if those attacks also use charges. For example, the air jab look insane; a huge amount of area is covered in front of him, it will completely cut them off from approaching. But it could also potentially burn through your book very quickly. This is supported by the fact that in both cases it looks like he does a very similar sword slash, although I had to pause at the exact right moment to see it before the wind jab.
I think this aspect will appear in more than just a jab; it might also influence other aspects of his kit. As for how the charges work, I have no idea. XD. That being said, he looks like he has some incredibly strong air game; an extremely gimpable recovery might be a weakness he has to endure if he runs out of Elwind.