But there are now significantly more unused trait options. What's the point of that?
When Conquests came out for Civ3, they redid some of the old civs too. I thought they might have changed more, but they did a decent job and made sure only two civs shared the same traits, while everyone else got new ones.
EDIT: Just to add to my previous comments. Aggressive, Expansive; Aggressive, Financial; and Expansive, Organized now have 2 leaders using these traits. At the same time (keeping in mind we still don't know 3 leader traits) there are now 25 unused traits. If Firaxis wanted the old leaders to keep their traits, I can't imagine that they would have doubled up on traits when there are so many to choose from.
I don't think they'll dramatically redo everyone, but I do think that three old leaders will recieve new traits. And, depending on the traits of Stalin, Rameses II, and Augustus, there might be three more.