The datamining community, especially when it comes to specific games, has come through quite frequently in the past five years. Even if it's just spotting a few file names here and there thrown in during prep work for upcoming DLC those folks are vigilant, always willing to comb over the most granular detail to locate an announcement here and there.
That's just what they've done with Xenoblade Chronicles 2, in an effort spearheaded by a community member named Moosehunter. In a recent compilation, and this is entering spoiler territory as was noted twice in the titles above, it was revealed that the upcoming DLC could deal with the Aegis War -- the grand event that happened before the events of the game.
Drivers (read: NPC companions) are out, and instead you'll be controlling Lora, Addam, and Mythra with their own statlines. It also may provide Blade gifts for the main game, including Shulk. This would all be part of the season pass if you already own it, and the first major story DLC for Xenoblade Chronicles 2 when it arrives later this year.
Of course this might be placeholder info, or junk data to throw users off the scent; but it seems highly probable that Monolith Soft would hone in on past events to give the DLC a bit more pizzazz and keep it separate from the massive storyline so that anyone can jump in at anytime.