I would defend as a Space Wolves fan, but I'll defend as an Orks fan: Personally, the Thunder Wolves might be dumb (in the "silly/impractical" kind of way), but the concept is pretty amusing (in a "haha" kind of way). Seeing a bunch of guys on cybernetic dire wolves running around--successfully popping tanks and slaying monstrous creatures--makes me smile (even when I'm not playing them); and I am a fan of anything that makes me laugh and/or smile. There are the other silly/dumb bits throughout the universe (not just in the Space Wolves): "Drive me closer! I want to hit them with my sword!" tactics actually working, everything Ork, Blood Angels allying with Necrons, the Ogryn just being Space-Ogres, and the Squats just being Space-Dwarves [*solemnly* We Shall Never Forget...]. In the end, Warhammer 40k is a Science Fantasy game, not a Science Fiction game. Blurring the lines between the two--especially in a less-than-subtle way--might chafe, but it's in the general theme of the franchise. Constructive counterpoint: introducing Thunder Wolves could help bring in the MMORPG crowd (with all their desire to buy more mounts)! Could that help broaden the audience?
Yeah, I heard about that --but one can dream they'll at least show up in the store sometime in the future! *Starry Eyed*