Blizzard have announced a new league for Starcraft II which will provide "the best players in each region a new arena in which to prove their skill", the Master League.
The existing Bronze, Silver, Gold, Platinum, and Diamond leagues each contain 20% of the active players in a region and the top 2% will be promoted to the new Master League. In their words, this is a league for the best of the best and will help recognize the talents of the most skilled StarCraft II players.
In addition to this they have further plans for a Grandmaster League which will contain the top 200 players in each region!
Further details on the Master League and a short Q&A can be found on the official post.