At the Valencia eSports Congress, lead developer of Starcraft II Dustin Browder was asked if there were any free to play plans in the cards. Browder did not make any statement to confirm or deny the possibility, but did say that Blizzard is "looking at free to play as an option for the multiplayer".
Browder further clarified that Blizzard would need to make sure that F2P in Starcraft II was feasible before they added it. “We don’t know how we would monetize it. While it might be good fun for me to play against someone with only half the units available to them, that’s not going to be an enjoyable experience for them."
"May I suggest hats on every unit?"
The idea of F2P Starcraft II could be an intriguing one in the eSports community. Starcraft II shares favorite status among the community with League of Legends and Dota 2, both of which are free to play. It's possible that Blizzard wants to increase their audience by going free to play, but they will not sacrifice the game's quality to do so.