The latest Fire Emblem: Three Houses Perfect Guide published by Famitsu contains interesting information on upcoming DLC for the game.
On one of the pages of the guidebook, the contents of the Wave 3 and Wave 4 DLC has fully been revealed. Both waves include free and paid DLC.
Spoilers incoming
Wave 3
- Free DLC
- New playable character: Jeritza (certain routes only)
- New support conversations [presumably featuring Jeritza]
- New activities
- New online features
- Paid DLC
- New playable character: Anna
- New monastery facilities
- New online [features?]
- Anna and Jeritza paralogue
- New quests (around 10)
- New activities: Sauna [who didn’t see this coming?], playing with dogs and cats(!)
- New costumes: Maid, Butler and more
- New battalions: Maid and Butler
Wave 4
- Paid DLC
- Side story: Abyss Mode
- New playable characters: Juris, Balthazar, Constanze and Javi [tentative translations]
- New support conversations
- New monastery facilities
- New online features
- New classes (4)
- New enemy monsters
- New hero relics
- New paralogues
- New quests
- New battalions
- New gambits
- New costumes for Byleth (male), Byleth (female) and Sothis
All in all that looks quite interesting right?