Back when the heads of Infiinity Ward left Activision, Sledgehammer games stepped up to fill their role in the two developer scheme that Activision had set up for the franchise. However, the plan was to have Sledgehamer move the franchise in a slightly different direction, with the new development team taking Call of Duty to the realm of action adventure games. That may still be the case, however, recent ads placed in Gamasutra reveal that the game will still be an FPS.
Although not much more is known about the upcoming installment of the best selling series, this does seem to be keeping in the two developer strategy that Activision employed in which both Infinity Ward and Treyarch were developing games for the franchise independently. Sadly, it also seems as if Activision is content to keep pumping out as many titles with the Call of Duty name on them as possible. Hopefully the folks over at Sledgehammer can bring new ideas to the critically acclaimed series to keep it new and exciting.