From the get-go, it's been understood that OoT3D will give a minor boost at release, with little seen in the long-term.
Just like almost every single other one of Nintendo's games, it's the legs that are going to count. Yes, the 3DS will see a bump when it first releases, but the greater effect will be the game's contribution to the 3DS library in general. With OoT3D added to the 3DS's repertoire, potential buyers will be seeing that much more value in the 3DS's library. It may not be the single aspect that sells most people on the 3DS, but it will help serve as the sixth or seventh reason for most people, helping to sell them on the system.
In the end, it WILL have major effects on the system's sales, but only as a secondary affector.
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