whos warchief now?

[Ninth Delegate]

It says in the small bio for each warrior that Swan dislikes the role of leadership, so I can't see him taking over after the film.
Snowball was originally mute for most of the movie, so I don't picture him as a motivational speaker to rally the troops.
Like Ranchgal says, It would be someone thats not in the film who would take over.