Shortly after the one year anniversary of the games release, Valve has announced that they are ready to release Portal 2's map editor, dubbed the Perpetual Testing Initiative.
Though most users will doubtlessly never touch the map editor (and those who do will probably be terrible at it) the 1% of decent maps will likely be enough to last even the most devoted Portal-fan until Kingdom Come (hence the title "Perpetual" Testing Initiative).
In other news, Valve also announced that Portal 2 has officially broken the 4 million mark. They did not, however, say how that number broke down from platform to platform, though we assume that most of those sales came from the PC version.
The four million sales mark is not entirely surprising though. Valve aggressively promoted the series through the release of Portal 2, sharply lowering the price several times across all platforms mere weeks after release.