The Wii and the DS were plagued with piracy in comparison to other platforms, but developers continued to support them strongly well into their late days. Why? Because a lot of people bought them. It's a self-winding wheel - people are buying a system because it gets loads of games and it gets loads of games because people are buying it.Ninty only gets money from licensing IF... companys decide to develope games for there systems AND IF people are actually BUYING them.
Piracy does not affect the equation substantially, it never has. In fact, the phenomenon of piracy is older than video games themselves and is always accounted for by the developers anyways. A developer will always aim to release games for a system with a relatively broad target audience to maximize profits, the 3DS already sold over 35 million units and it's not going to stop - it's going to be like a boulder rolling down the side of a mountain, gradually building up speed as more games are released for it. Whether or not 1 million of those 3DS users will pirate doesn't matter - the developer can still potentially sell several million copies of the game.