I would assume Kanade gets her position back really as we haven't seen any other Student Council members and the NPCs would have a tough time choosing one since they have to be practically perfect.

The 4th Guard Skill is Kanade making a clone of herself, I forget what the name of it was, but from the computer she can make a copy. Though it might be that she's still devloping it or something like her next idea on the computer.

She should make many more version of Hand Sonic though.