RPG Vault - The Evolving Face of Gaming
Not particularly RPG-specific but RPG Vault has a developer Soap Box editorial with PlayFirst's John Welch (Diner Dash, which has apparently sold 2M copies) discussing the tags of "casual" and "hardcore" gamer:
Interestingly, where casual gamers have been traditionally viewed as people who occasionally play solitaire on the computer, and core gamers are the select few who are really devoted to their games, we are now seeing these roles merge. Casual audiences are behaving like core gamers - playing longer, later, faster and demanding smarter games - and core gamers are enjoying less hardcore experiences, as demonstrated by the popularity of titles like Wii Sports and Guitar Hero. Our research suggests that casual gamers are starting to do what core gamers have done for years, adopt and grow communities around their favorite content experiences.