I got that katana from the vid, but so far you either get it as normal quality or u can get the legendary one from the cyberpsycho which might always be the same grey one. Saw my katana on the ground had like an epic icon but when hovered over it it is a normal one (maybe a bug). As for the Arasaka one from the trailer, is not in the game "yet". Not gonna give false hope, maybe they'll bring it in an update/dlc as an iconic one.
If you want a thermal one u gotta save before fighting one of either the tyger claws or arasaka guards -when they have their katana out- and hope for a katana with thermal damage if not reload from the save and try again, u can also go for color there.
People claiming they have seen a weapon mod drop, I have so far not seen any of those mods. Katana with the specific elemental damage already onto it yes but mods nope.