They've done this before IIRC, with confirming they have more titles than they have announced, and then announcing the others before the show.
Namco Gamescom Game Line-up:
Source: https://en.bandainamcoent.eu/news/bandai-namco-entertainment-europe-reveals-gamescom-2018-line
Namco Gamescom Game Line-up:
- Jump Force
- Soul Calibur VI
- Dragon Ball FighterZ Switch
- One Piece World Seeker
- Code Vein
- Ace Combat 7: Skies Unknown
- My Hero One's Justice
- Naruto To Boruto: Shinobi Striker
- Mystery Game #1
- Mystery Game #2
- Mystery Game #3
- Unclear if one of the above mystery games or not: "We're also proud to announce a brand-new co-publishing project at the show we think our fans will be very excited about. Stayed tuned for more information."
Source: https://en.bandainamcoent.eu/news/bandai-namco-entertainment-europe-reveals-gamescom-2018-line