PC gamers should be used to this by now as Assassin's Creed IV: Black Flag is slated to be released after the console versions. So, what's the excuse this time? Lead Designer for the game, Jean-Sebastien Decant, explains why.
"It all depends on what is the master version," Decant said. "If for instance, the [Xbox 360] version was the master version, or the PlayStation 3 version was the master version, then we'd need a little bit more time to adapt it for the PC. But we need to finish that other version first."

Both the Xbox 360 and PlayStation 3 versions of the game are considered to be the "master version." So, the focus remains on those consoles before being shifted elsewhere, say to the PC version. This might be the first time a non-BS reason was given for why the PC version of a game is coming out later.

Don't feel too bad though. Decant also said that the same principle applies for the next-gen consoles. They too will trail behind the current-gen versions of the game as far as development status is concerned. I wouldn't expect that to be the case in the future, however.

(via Polygon)