In a recent visit to Australia Gabe Newell has stated that "I thought Left 4 Dead 2 would get the same treatment as Left 4 Dead 1," said Newell. "So I was a little surprised by the Review Board's decision]." Apparently the Review Board had a different plan but in the end there seems they reached a mutual understanding.
“It's a game for adults. But we're aware that different countries have different restrictions, and we want to make the choices that make the game the most fun for that country.” As expected Left 4 Dead 2 will be released in Australia.