Downey Jr first donned the character in 2008 when he filmed "Iron Man".
The news was announced by Marvel Studios bosses but there was notably no mention of an "Iron Man 4", reports femalefirst.co.uk.
"The Avengers 2" is expected to hit theatres in 2015 and will see Downey Jr reteam with Mark Ruffalo as Hulk, Chris Hemsworth as Thor and Chris Evans as Captain America.
Photos: Kareena Kapoor Khan and Aamir Khan at Mumbai airport
Photos: SRK, wife Gauri, Aishwarya Rai, Shweta Bachchan at Vogue Awards
Photos: Harbhajan Singh-Geeta Basra's TV outing with daughter Hinaya
Photos: Malaika Arora flaunts ripped jeans like a boss!
Photos: Vaani Kapoor, Kriti Sanon, Dia Mirza sizzle on the ramp