Last time L5 announced a game with no platform was TT, and it turned out to be 3DS (with PSP/Vita ports). Ghoul Watch seems like Wii U given the quality of the visuals, plus the "second screen" ghost catching seems like it's tailor made for the Gamepad.
I also used to think it could be Vita, but the way things are going now, even if it was at one point I doubt it is now.
This game will absolutely crater. These cross media franchises rarely ever gain a threshold on consoles. I don't mind since it's one step closer to Dark Cloud 3.