World of warcraft game director on how to upgrade an insanely popular franchise

You've got an incredibly popular game. You need to create a new version, but you don't want to lose what made the game so popular in the first place. How do you do it? That was the basis of a talk delivered by Tom Chilton, Game Director for World of Warcraft, an insanely popular MMORPG by Blizzard.

The talk resonated with his audience of developers because they're all facing this issue. Chilton said that no matter what stage of development you're in, you're usually working with some form of existing IP. When you're in that situation, you want to retain the soul of the original and carry it into the new version you're creating.

Watch out for small cascading changes that ultimately change everything, advised Chilton. Instead, divide it up. Keep a third of the old, improve a third, and make the last third new content.