The first teaser poster of Kamen Rider W revealed a few weeks ago showed the silhouette of Black (in my opinion) with, ahem, a V Fin - more accurately, the character 'W' for non-Gundam fans on his forehead.
A few unconfirmed photos show his costume design and bike:
It's a dead giveaway from his costume design that he would have form change just like Den-O and Kiva, but this time the colors are swapped on half of his body only. Not sure how that works actually, because then it would seem like he has plenty of options, like red on the left + purple on the right, the other way round, green + purple, purple + green, or maybe red on both sides, purple on both sides?
We'll have to wait a little longer to know more about him. ^^
All images from Toysdaily.