It says in the description of the new edition that:
This Core set is best suited for a group of four players – one Game Master and three Player Characters. Adding more players is easy! You can find more careers, party sheets, action cards, and components in the the Adventurer’s Toolkit.
So what is this Adventurer’s Toolkit - a expansion on or what?
It also seems from this that you can play more than 4 people, and I gues that you can play more than for with the core rules if you use your imagination. There it was again that important word for RPG - Imagination...