It was revealed back in June that season 3 of A Certain Magical Index would be premiering this fall and we finally have an exact date - October 6. It's been 5 years since season 2 ended, though a spin-off series, A Certain Scientific Railgun, has released two anime seasons in the interim.
Previously confirmed key staff members include Hiroshi Nishikiori as director, Hiroyuki Yoshino as series writer and Yuichi Tanaka as character designer. The Twitter account has more recently confirmed Tomonori Kuroda as art director, Shingo Fukuyo as director of photogray and Maiko Iuchi on the score.