I'm having a lazy Sunday so lets speculate on what heroes could be about.
I see a good number of possibilities for this expansion
1. Antonym to epic BattleLore
The expansion will shrink the scale of battlelore. Unit figures will no longer represent massive numbers of troops but will become one to one representations as the game shifts to squad level combat. The change of scale would facilitate adding powerful new heroes to the game, who would act individually both powerful in combat and granting unit bonuses (easily tracked with hero banners that plug into the banner hole of the unit figures) in thish situation your counsle members would also become hero figures and would likely keep a few reusable lore cards.
2. Guest counsel members (most likely)
The expansions will provide a number of characters that can be added to the guest space in the war council. Like creatures these will take up counsel levels but instead of lore deck mastery they will be pieces on the board. The heroes will act in unison with units granting special abilities to them. While the hero's will be able to move from unit to unit they will be unable to combat alone.
I could also imagine the expansion adding more role playing elements but i'm not sure how that would work.
What do you think heros will bring?