I wasn't aware there was any doubt that a 3rd EverQuest game was in development. Crabbok, you doubt my sources? 
Yep, that's a few quotes out of the last chapter in the 10th anniversary Everquest book that was available at Fan Faire in June. Kind of an old news story, but I digress. 
There is no doubt it will be a PS3 & PC game, with players able to interact with each other across the platforms. All SoE MMOs currently in development (Agency, DC Universe Online) are PS3 & PC.