According to a report from Develop, Blizzard is working on an unannounced free-to-play game. A source "connected to the matter" says the company has already started a free-to-play project, seeking to expand their offerings to both "fremium" and subscription-based titles, but could provide no further details.
While Blizzard has declined to comment, this would not be the first time the topic has come up. At BlizzCon this past October, Blizzard COO Paul Sams commented on the free-to-play model, stating that while it was possible under the right circumstances, they did not have any firmly established plans to adopt it themselves. Given that was only six months ago, this project is likely in its infancy at best. You know, if it exists (please don't hurt me, Blizzard lawyers).