I have the DS and Wii game pre-ordered at GAME and got my order cancelled today. I've also noticed neither game can be pre-ordered at Amazon, which makes me wonder if this will get a UK release (or any release at all!)
Activision are the publishing company with all the rights and they have sub-contracted the license by platform for the movies and other things like War for Cybertron (Cybertron adventures on Wii) and the DS games.
They showed a trailer for the Wii game at Botcon and suggested that like the Dark of the Moon game, the 3ds/ds games would be effectively identical. So the Prime game doesn't appear to be vapourware, just not really advertised much.
I haven't seen anything official suggesting a cancelation, but GAME not stocking it could imply that its cancelled/delayed OR that Activision don't want to deal with GAME (despite GAME being in their post-bankruptcy status they are still something of a mess)
I've not really been following Prime news, but at the recent Wii U announcement event thingy, Prime was shown as a Wii U exclusive. Could be that the Wii version has been scrapped in favour of Wii U, with handheld versions scrapped or postponed for awhile.