Battleblog #5 on the Battlefield Blog talks about the unlocks and rewards in Battlefield 3, saying there are "years worth" of such perks to be earned in DICE's upcoming military shooter sequel. Here's a bit:

Back in 2005, Battlefield 2 was one of the first shooters to introduce a deep persistence system to add that extra layer of tasty rewards and unlocks to keep players returning to the battlefield for hundreds of hours. With Battlefield 3, we are pulling all the stops. Compared to Battlefield: Bad Company 2, Battlefield 3 will have more than 10 times the hardware unlocks spread over weapons, weapons attachments, gadgets, and a huge unlock tree for vehicles alone.

Skill and dedication equal rewards
On top of these ingame hardware items, players will also be richly rewarded with medals, ribbons and service stars displaying their skill, commitment, and teamplay prowess. You will be rewarded handsomely in Battlefield 3 for exemplary skill, such as capturing X amount of bases in one round. Excellent teamplayers who keep the team’s vehicles in mint condition and revive fallen comrades will not go unnoticed either. These type of skill-driven rewards are typically handed out in the form of ribbons, and good players can often get more than one ribbon in a single round.