I don't get the whole "I want a new one" attitude. Of course you're going to get a new one, regardless of whether or not we get a Majora's Mask 3D. Grezzo would likely develop Majora's Mask 3D while EAD works on the new 3DS Zelda. And honestly, I find it highly likely that we will see a Majora's Mask 3D. Think about it - Ocarina of Time 3D proved to be a massive success for Nintendo, selling more 3DS hardware units than had been previously sold. The sales of the game itself were likely enough to warrant the production of the game, and the added bonus of boosting 3DS sales is icing on the cake.
So imagine a year or two down the line. The 3DS has a nice catalog of games, such as those announced at E3 - Luigi's Mansion 2, Mario Kart 3DS, Paper Mario, Super Mario, etc - big games that people are going to really want to play. The 3DS is likely going to have seen a price cut by that point as well, so the units are moving off the shelves pretty swiftly. Nintendo is set to release a brand new Zelda game sometime in the future. This moment would be perfect to launch a Majora's Mask 3D - considerably less production cost, given the prebuilt interface and engine; legions of fans from the classic N64 era (us, in other words), and legions of new fans converted by OoT 3D. Nintendo suddenly has a nice hit on their hands for a comparatively cheap production budget, and they are set for a brand new Zelda game not far into the future.
I don't see any way that making a Majora's Mask 3D would be anything but a huge profit for Nintendo.