"World of Warcraft has been such a central part of my life these past six and a half years, and it's success would not have been possible without the tremendous community around it, so I wanted to say thank you to all our players who've shared this amazing experience with us so far," he wrote in a forum post noticed by WoW Insider.
Kaplan noted that he still plans to be involved in World of Warcraft's future, adding that "partners in crime" Tom Chilton and J. Allen Brac will now handle day to day operations.
"When all is said and done, WoW is still my favorite game. I play it every day. None of that passion is gone," he concluded. "If anything, it fuels the challenge of making our next MMO even better. We know we have some big shoes to fill."
As of late December, World of Warcraft had 11.5 million active subscribers worldwide.