So first thing is first, the current S-400 is rumored to just be the S-300PMU3, that was renamed for convenience reasons. This makes sense technically, since the system is the same, with only changes in the form of a single new munition, and new radars. It's a deep modernization rather then a new system. The S-500 is supposed to be an optimal air and space defense system that combines tactical BMD, and GBAD into one package.
Second off we have no specific info. I seriously doubt that 2012 is a realistic IOC date. Especially given Zelins recent statement in regards to his dissatisfaction on the work on the system.