HBO confirmed during their TCA panel that Game of Thrones will premiere in the spring of 2011. One executive actually gave a date of March 3, 2011, but another corrected him and said just spring 2011:
“It’s a genre we’ve approached somewhat cautiously,” said Michael Lombardo, HBO’s programming president. “We have two writers … who are so smart and so talented. Neither of us are particularly fans of the genre. It was such enormously compelling reading. It wasn’t the genre we responded to it was the storytelling.”
“It’s really about power,” added Richard Plepler, co-president. “And that’s a theme which has resonated throughout history. You’ll forget where you are very quickly and will find yourself immersed in the storytelling.”
Source: the live feed