That'll be pretty tough if Nintendo continues to release games. The bar will only be raised higher (Wii Sports Resort should make top 5). MH is the only game I see with a chance.
Still, it's important to remember how the top 10 DS games looks in Japan:
- Pocket Monsters Diamond / Pearl
- New Super Mario Bros.
- Brain Age 2: More Training in Minutes a Day
- Animal Crossing: Wild World
- Brain Age: Train Your Brain in Minutes a Day
- Mario Kart DS
- English Training for Adults
- Pocket Monsters Platinum
- Mario Party DS
- Nintendogs
Nintendo has been dominating all of Japan, so it can't be helped. If not for MHF, the entire top 17 selling games of this gen in Japan would be in Nintendo's control.