Hey Talisinbear, great that you are interested in the game!
I try to answer your questions as concise as possible:
1) Yes, a campaign mode is already under development!
Besides, there might come some campaign books detailing specific areas and happenings, providing everything to play out these conflicts, including special rules and models.
2) They are. To be honest, a whole wave of future factions is already decided on. However, the initial 6 factions need some more attention first.
3) Well, this depends on faction, troop types and battle level (the amount of points to spend for warband composition). You can have a fast starter box game (around 160 pts) with 5 models (Troglodytes) to 8 models (eg Halodynes or Wyldfolk). Engagements with a battle level of 300 pts can vary considerably in terms of the number of models, but often see around 15-20 models for human factions.
There will be 12 initial releases of every faction for wave 1 (hopefully all released until late summer). Wave two will see another 12 releases for each faction. Some of these releases will be single characters or creatures, other units with multiple models.