Yes folks, the rumors are confirmed. From Friday, 6:00 AM on May 24th to 6:00 AM on Saturday, May 25th, Disneyland will not close.
A Disney Parks representative announced the summer celebration last night in Orlando. The Magic Kingdom parks in both Disney World and Disneyland will be open for 24 straight hours, as well as Disney's California Adventure.
This is a rare chance to experience Disneyland past midnight, although last year they had a similar event. No word yet on what facilities and attractions will remain open for the full 24 hours, but I imagine the cast member situation will be all-hands-on-deck.