Call of Duty: Modern Warfare Progression Details

Activision Games Blog discusses changes to player progression in Call of Duty: Modern Warfare, saying the military shooter is replacing the Prestige system with seasonal ranks (thanks MP1ST). The post goes into great detail, so here's the brief introduction:
Call of Duty: Modern Warfare is set to offer a fresh progression system that gives players a constant stream of rewards while keeping the satisfaction and pride that comes with ranking up.

In Modern Warfare, you will unlock loadout options, Killstreaks, and Field Upgrades through an initial series of Enlisted Ranks, earn permanent rewards and icons through Seasonal Officer Ranks which are memorialized permanently, and unlock an arsenal of attachments and camos through Weapon Levels.