Ok, so as I've seen, and experienced, the quest for Reunification of Skyrim, can be buggy, and somtimes to the point where you can not progress further, because the characters will not give you the necessary dialogue to respond to. I spend about an hour (IRT) trying to figure it out, when someone suggested I go talk to the Jarl of Whiterun after the battle for Whiterun.

If you should try to talk to Legate Rikke, and she will not give you the dialogue, go back and talk to the Jarl of Whiterun, and then go back to her. If anyone is still having this bug, let me know if this helped, if it does not I will request the thread to be renamed as "One solution to the Reunification of Skyrim BUG" I don't want to be misleading...