World of Warcraft, one of the most successful online games of all time, currently has a subscription fee which allows you to play the game. But according to World of Warcraft's lead designer Tom Chilton, in an interview with PC Gamer, "at some point, it may not make sense for us to have a subscription fee."
Blizzard is considering the free to play model in response to the other online games that have moved away from the subscription model and adopted the micro-transaction model. Rather than charging a subscription fee, many of the more valuable items in the games are purchased with real money rather than being found or purchased with in-game money. Having users purchase items in the game with real money helps to offset the subscription fee for the service. Games like Lord of the Rings Online, Company of Heroes and Dungeons and Dragons Online have all moved away from subscriptions fees and are now making their money through micro-transactions.
Blizzard isn't feeling any pressure to move to a micro-transaction model just yet though and they don't feel the games that have gone free to play really competed with World of Warcraft. Tom said, "I feel like they’re doing that to compete with other games that are on a similar subscriber level to what they were at. I imagine that when one of them went free to play it cannibalized some of the other subscribers. I can definitely imagine that being the case with World of Warcraft. If another game comes along and blows us away it may not make sense for us to have a subscription fee. Or even further down the line, when we have another MMO out."
The micro-transaction model is certainly a viable one for Blizzard as there are even several companies, such as Nexon and Ijji, that offer all of their games for free and are funded entirely on micro-transactions. But don't expect World of Warcraft to move to a free to play model just yet. According to Tom, "We’re not spending a lot of time thinking about it. It’s not something that’s a reality for us in the near future."