Portal 2 has done quite well since it launched just two months ago. Co-founder of Valve Software, Gabe Newell, announced the sales figures at the Games for Change festival earlier today. Accounts of the announcement claim Gabe did not provide any specific details about the sales figures. Whether this number includes digital sales via Steam as well as retail was unclear.
It’s hard to measure Portal 2’s success at this point. We do know that the original game sold over million copies in the physical form, with many more likely sold over Steam. Valve will likely host deals for the game via it’s Steam distribution service so the game will likely continue to sell for years, especially if Valve and the Steam community support the game with add-on content.