I believe the diecast has been confirmed (we know the molds exist to do so because of Black Convoy). The reason Mirage was clear plastic was probably because Takara never made the molds for diecast parts - these molds were completed for Convoy because he was only a couple of months away from release when the plug was originally pulled on BT.
i never thought it was supposed to be green... are we even sure it's diecast?
So we're getting a die-cast Prime now instead of the green one? Lame :tfsad