A port of Majora, made by Grezzo and using the same engine as OoT 3D could be out much faster than a completely new Zelda though.
I can see them wanting to enlarge the catalogue of the console a little, by having that game out ASAP... I know it's not a complete desert in terms of games on 3DS, but one must admit that, given how much longer it takes to develop a 3DS game compared to a DS game, and how much more expensive it is also, the 3DS library isn't expending as fast as the DS one.
So even if it's just one more game, and it's easy to port and could be done fast, they have all the reasons in the world to do it (especially since the audience is there to receive it, fans have been asking for it for a long time after all).