What Nintendo did with wm+ and Zelda was what in Spain we call "lanzar un globo sonda" and it's something politicians use to do (and please forgive me for this comparison): when they have an idea but don't know how well received it will be among yhe people, they just say that they are studying it and way for reactions. Nintendo announced that they were studying the use of wm+ and people claimed how good it'd be, reinforcing their original plan (if people's reaction were against it they could go back to simple wiimote).
As for the lack of good 3rd party games with motion controls it's only the result of the lack of support from them. No games in general means no games with motion controls in particular, and even less with a good implementation of them.
In the end, Nintendo has said that they want to improve and expand the way we play games, and you don't do that introducing motion controls with one console just to take them away with the next one. Also they have launched the 3DS with motion controls, why would they ditch them in Cafe?
The problem with your theory is that Motion + has been out for a while and the new Zelda is still a ways away, why the hell havent they been supporting it all this time??? Wasnt the test Wii Sports Resort?? Where was the followup?? Flingsmash???? Even the damn Move gets more support and that thing doesnt have near the install base of Motion+. So yeah I would be surprised if they did ditch it