In a further follow-up to concerns expressed over potential Battlefield 3 balance issues resulting from preorder bonuses, the Battlefield Blog now offers reassurances that the Physical Warfare Pack preorder bonus for the military shooter sequel will eventually be a free release for all players (thanks Brady). Here are excerpts on how both pieces of preorder DLC will be handled after the game's release:

I would like to start by clarifying that the Physical Warfare Pack is a time-based exclusive. If you do not pre-order Battlefield 3 at a retailer carrying the Physical Warfare Pack, don’t worry. We will unlock the contents of the Physical Warfare Pack for free to all Battlefield 3 players later this year.
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If you pre-order Battlefield 3, you will be able to play Back to Karkand at no extra charge as soon as it is released, but it is not day one DLC and it is not on the base game disc. We think it’s a sweet deal, and it’s available to everyone everywhere. If you do not pre-order Battlefield 3, you can still buy Back to Karkand separately and play it as soon as it is released, the very same date as anyone who pre-ordered. In other words, there is no segmentation of the community when we launch the base game.