Well, the video said he has his Levin sword because he runs out of uses on his tomes. Levin Swords are capable of casting magic (thunder only). I may need to see a little more of Robin before I fully understand the Sword changing.
I assume one special is relegated to casting spells while another is for switching tomes. Probably Standard and Down specials respectively. Charging with a tome will likely give a more powerful version of the spell and the Tomes will likely only be of 4 types: Thunder, Wind, Fire and Dark. As having to switch between everything would be rather absurd. If there weren't 4 types, I would think this was part of his customizable sets.
As for movelisting what we've seen:
1:17 Down Tilt
1:19 Combo, which appears to end with a spell from the currently equipped tome.
1:22 Grab, which appears to use some sort of magic I'm not familiar with.
1:23 Back Throw, a ball of magic briefly appears.
1:25 Taunt 1
1:27 Standard Special, Thunder
1:29 Standard Special, Elthunder
1:30 Standard Special, Arcthunder
1:32 Standard Special, Thoron
1:35 Standard Special, Arcfire
1:37 Down Air, Elwind (perhaps it changes based on what you have equipped?)
1:39 Standard Special, Nosferatu
1:41 Standard Special, Arcwind (I believe, no name given)
1:49 Forward Air, appears to have Dark effects as well as electric effects (curious)
1:50 Taunt 2
So, my prediction is Standard Special is "Cast Spell" and Down Special is "Choose Tome."