I went shopping this weekend and I still saw "Limited Edition" Battlefield 3 copies on store shelves so there's no reason you'd need to pay for the upcoming Back to Karkand DLC map pack.
Even if you managed to miss out on the first-run freebie, it seems like these classic maps will be worth it, especially if you've ever bought a Call of Duty map pack. Gulf of Oman was personally my favorite map, although I know Karkand is pretty highly regarded among Battlefield's player base.
Back to Karkand is still scheduled for December 2011 with PS3 gamers receiving the pack one week early.