As we reported on March seventh about the possibility of the 'Mushroom Kingdom Hearts' game in 2008, new news comes about. This was, accordingly, just a April Fools joke and a rumor. Kotaku mentions that the game WOULD have featured 41 Nintendo characters which results to 4/1 aka April 1st.
Also as evidence, Mario is shown without the "M" on his hat in the so called promotional game poster. Sorry folks but this news had to be broke.