According to friends at the website Unleash The Fanboy, they have a source at Disney who has told them not only is JARVIS voice actor Paul Bettany returning to his role as JARVIS but he will be Ultron's voice because JARVIS is Ultron. Whoa. This means everyone who thought Stark would be Ultron's creator was right.
More specifically, UTF's source mentioned Bettany has signed a new contract. If all true then look for the voice actor to possibly portray the villain in more than just in Avengers: Age of Ultron. Whether this lines up to what really happens 21 months from now when the Avengers sequel hits theaters is unknown but for now, this is the latest rumor to come out of the rumor mill.
Click right here to read Unleash The Fanboy's entire report about this new rumor.