User blog comment:Dragonfly18/Battlefield 3 multiplayer trailer/@comment-4092147-20111019231553/@comment-24476373-20111021211711

If you pre-ordered BF3, then you get Back to Karkand on Day 1 for Free.

Also, there is a possibility that there will be EU vs. PLA or EU vs. MEC, as there are 10 weapons added in Back to Karkand (Which, if you get them, can also be used in the base game), and they seem to be weapons that they would use, including the L85A2, the HK53, the PP19 Bizon, the MG36, the FAMAS F1, the Jackhammer shotgun, L115A3 (I think they called it the L118), the QBB-95 (Called the Type 95), the QBZ-97 (Called the Type 97), and I think they also said the AW50.