According to a survey that reached Kotaku, Activision are entertaining ideas of a Guitar Hero: Red Hot Chili Peppers. Even with Activision scaling down Guitar Hero releases this year, it would make sense with a Chili Peppers specific title given their long career and numerous hits.
The following is a quote from the survey:
"Celebrate the entirety of the Red Hot Chili Peppers' life, starting with their early days in LA, to their famous Hyde Park concert to their highly anticipated new studio album. Discover the story behind their legendary music as you unlock interviews, retrospectives, concert footage and other commentary."
The survey makes specific mention of By The Way, Californication, Give It Away and the Red Hot Chili Peppers' "upcoming studio album to be released in 2011". The latter seems to indicate that we won't see a potential Guitar Hero: Red Hot Chili Peppers until next year at the earliest.