This doesn't seem like anything TOO special. It's more or less the company knowing that their product is going to be hot, and people who get interested are going to spring more cash on another game, whether they'll be going from DS to PC or PC to DS.
It's win/win for the company.
By life end:
- Wii- 100 million+
- Xbox360- 35~40 million
- PS3- 30 million
- PSP- 30~32 million ------------- FAILURE
- NDS- 85~90 million (Skeptical) - FAILURE
- NDS- 100 million+ (Optimistic) -- Success!