Call of Duty: Ghosts has recently launched and it's no surprise that Activision is doing a Double XP Weekend to celebrate. Beginning yesterday at 10am PST and going though Monday, November 11th at 10am PST, players on all platforms will earn twice the amount of XP for all of their multiplayer actions. More info can be found on the Double XP Launch Weekend FAQ.
In addition, players thinking about upgrading to the PS4 and/or Xbox One versions of the game can play now and upgrade later. All of their Multiplayer XP, stats, and achievements earned on the current-gen consoles will carry over to the next-gen consoles when they upgrade (assuming you go from PS3 to PS4 or Xbox 360 to Xbox One of course). More info on that can be found on their next-gen upgrade page.