Stated in the PC Gamer, an interview with a Mod team is making a total conversion for Warcraft 3, and they've talked to Blizzard and such.
In the article, it said Blizzard was in a lawsuit, didnt state with who, but Gamesworkshop sued Blizzard for copying models/ideas, the whole Gamesworkshop franchise.
So thats why StarCraft 2, which was in production in 2003 was stopped due to the law suit.