Yeah, I think he will be playable.
Also, for that Toadette guy, here's proof of her. http://mariokart.com/wii/
The first video, you can see her easily. That's also the official American site I believe. Tomorrow a tour across USA starts, you can see the places on the site.
http://www.vgchartz.com/games/userreviewdisp.php?id=261
That is VGChartz LONGEST review. And it's NOT Cute Kitten DS