This one is a no-brainer. We already know that DLC packs are coming (we even know what's in the packs), but it seems obvious that we will get a real look at them here.
DLC Pack 1 will come with new armor, a new challenge mode titled Trial of the Sword, a hard more, Hero's Path Mode (which allows you to track your path throughout the world), and a Travel Medallion that allows fast travel. I wouldn't be surprised if this was briefly discussed, then announced to release then and there.
The second DLC Pack is the more interesting of the two, as it comes with a new dungeon and new story content. Nothing more is known about this DLC pack as of now, but following the release announcement of DLC Pack 1, I would expect a trailer for DLC Pack 2. This would give fans a reason to go back to Breath of the Wild, as well as stay excited for the title for the remainder of the year.