It has been announced that Infinity Ward and Treyarch are being joined in the development of the Call of Duty series - Sledgehammer Games.
Sledgehammer Games have worked on the CoD series before, aiding Infinity Ward in completing Call of Duty: Modern Warfare 3 and making DLC for it with Raven Software. They will be releasing this years installment of the franchise, giving the other two developers three years rather than two, to create their own.
Sledgehammer Games has not released any of their own titles since their formation in 2009, though their having helped Infinity Ward to finish on time after staffing troubles is probably what helped them get chosen.
With three years to create their next CoD game, rather than two, it should mean that Treyarch and Infinity Ward's titles are much more polished. Although there has been no word on how long Sledgehammer have been working on their title.