Mark May 15 on your calendar and make arrangements to stow the kids at the babysitter’s for 30 hours or so, because that’s when Diablo III is finally coming to PC and Mac.

“After many years of hard work by our development team and months of beta testing by hundreds of thousands of dedicated players around the world, we’re now in the homestretch,” said Blizzard’s chief executive and co-founder, Michael Morhaime. “We look forward to putting the final polish on Diablo III over the next two months and delivering the ultimate action-RPG experiences to gamers on May 15.”

The Diablo games have enjoyed consistent success since the action role-playing series debuted in 1996, with over 20 million combined copies sold, and over $800 million earned at retail. The almost-guaranteed success of Diablo III should bring some relief to Blizzard, which has been hemorrhaging World of Warcraft subscribers over the past year. In fact, Blizzard is offering a free copy of Diablo III to anyone who pays for a WoW annual pass, provided they pay up by May 1.

For everyone else, Diablo III will cost $59.99 USD for either the retail version, or for a download. You can also pick up the Collector’s Edition for $99.99, which includes a behind-the-scenes Blu-ray, a soundtrack CD, a 208-page art book, a four-gig Soulstone, and a Diablo skull base that is guaranteed to freak out your grandmother next time she visits.

Stay tuned to Gamezebo for more Diablo III news.