FCS is a Warfare system geared towards employing new and improved warfare capabilities, tactics/strategy. Not a Tank [I am not sure if you understood].
I looked at the first link but didnt find anything concerning MBTs. I wonder if the hand wringing over Heavy VS. Light has left a future MBT out of the planning.
My mistake. Technically not a tank, FCS is an armored vehicle. As for MBT, I don't think there is anything on the boards to replace the M1. Sadly, I think the tankless-army people have gotten their way.