so avatar items are available for sale with gear from characters in MW3. the costume outfits include british, french, and russian special forces, as well as the american special forces in a scuba outfit. you can try them out on your avatar here. this confirms that the juggernaut outfit is exclusive to preordered hardened editions.
other companies are already releasing their preorder bonus items as well. on amazon, you get the american special forces armor for preordering (any tier). so far they are the first retailer that i can find at this moment to have an announced avatar outfit preorder bonus, ill do my best to update this thread if i hear of more.