I firmly believe that ToTK will not have a Direct on its own. It's not the type of game that you want to know every tiny detail before buying it, unlike others like Splatoon 2/3, Xenoblade 2/3, Animal Crossing, Mario Maker or Super Smash Bros. If you pay attention, you'll see that the majority of dedicated Directs are about games mainly focused on multiplayer or without a traditional campaign, the only exception being Xenoblade due to the complexity of its sistems.
Nintendo doesn't decide if a game deserves a Direct looking at its importance or scope. Look at games like Mario Oddysey, Luigi's Mansion 3, Metroid Dread, Paper Mario TOK, Bayonetta 3...They clearly weren't any less important than Xenoblade 2 and 3.
The most probably scenario is a full trailer + a Treehouse playing a demo of the early game like what happened with BoTW in E3 2016. But dedicating an entire presentation to the game?I don't see that at all.