Sony would be crazy to release both GT5 and the motion controller at once. People do not have that much money (GT5, DFGT, PS3, Motion Wand, PS Eye etc).
If you can spend money on all that, the wand would make little difference on your budget. Besides, the wand is totally unrelated to GT5 (not going to be used in the game) and basicly is for another target audience.
So all this talk about how this delay might be linked to the delayed wand sounds very unrealistic to me.