What could any ideas be? I am having trouble of thinking of a game that takes place after Redemption. I could only think of Jack avengeing his father by hunting down the survivors of those who killed his father, but since it's up to a choice who the player killed, in some games Archer lived and in some other died. In some the Captain died and others he lived, so that would be hard to do, unless they want to make one side the canon version, but it most likely be a spiritual succesor, not a sequel.
Another thing, it would most take place afer Revolver, but before Redemption. But who else would think an LIVE arcade and whatever PSN people have, where half of it playing as John as an outlaw, and the second part is Jack chasing down Archer for helping kill his father.