Ok, I can be a bit of a vigilante at times...but to my knowledge, Pokemon, Nintendo, and Game Freak have not put out a Pokemon Diamond game to this date, and the real one comes out in September in Japan, for DS only...
But, I do remember the old Rom from the internet a few years back before G/S/C came out, and it had nothing to do with the Pokemon I know and love...
Yet, people are selling it on Ebay...ok, maybe I shouldn't let it bother me, but now I see one with a box and instruction book...wtf?
http://cgi.ebay.com/Pokemon-DIAMOND-...ayphotohosting

EDIT: Now I have seen evry friggan thing...a crudely done Pokemon Pearl too...with a fat Pikachu and Ash...
http://cgi.ebay.com/Pokemon-PEARL-Ga...ayphotohosting