From WWE.com a few hours after John Cena’s statement on Twitter about his arm injury:

The information published about John Cena’s recovery was given to WWE.com prior to surgery. In speaking to Dr. Andrews after the procedure, in light of the amount of work that needed to be done and the number of bone chips removed, the prognosis for recovery is closer to six to eight weeks. Knowing John Cena, the former WWE Champion will do everything he needs to get back in the ring as soon as possible.