What Happens If The Sorcerers Run Out of Tokens?
The rules address that specific case in the section on picking a race (page 3)


  If, on the other hand, a Special Power (or Race power) lets you take
  additional Race tokens from the storage tray during the course of the
  game, you are still limited by the total number of tokens physically
  available. So a player with 18 Sorcerer tokens on the board won't be
  able to use his Sorcerer power again until some of his tokens become
  available.