Quite a confusing example since the game is based on characters being healers who have professions. New crafters coming into the game will have to level up their crafting skills which they can do by crafting things people need. Unless you meant when new professions arrive in future patches? I'm sure players will eventually have more than one healer and won't need to reset their profession to learn a new one.
There's also cooldowns for each profession, if a top forger who has the schematics/plans to craft something end-game people always want is busy crafting that daily for a queue of people wanting it there's room for others to craft something lesser or for other professions to try and match his skill level to get in on his demand. Obviously not everyone will have "work" and be able to earn zing from their professions, it'll depend on demand and how many don't bother to level up their professions or choose another one, etc.