A tweet from Sledgehammer Games co-founder Michael Condrey suggests that Call of Duty: Advanced Warfare multiplayer will have 50 ranks and 15 prestige levels.
Condrey"50/15. #7".of what looks like a prestige level symbol, alongside the numbers
The #7 seems to refer to the prestige level logo in the tweet, while Condrey has suggested before that the Advanced Warfare team was looking at prestige levels in the 10-15 range. Looks like they've settled on the latter number. That's a bit more than the usual number of multiplayer ranks COD games have for you to work through.
Prestige is earned once you've fully leveled up in multiplayer. It resets your skills, weapons and gear and makes you start the process again with only a shiny new logo to mark your progress. It's for masochists, basically.
Call of Duty: Advanced Warfare is coming to PC and consoles this November 4.