Rise of the Tomb Raider is exclusive to Xbox platforms, Crystal Dynamics Head of Product Development Darrell Gallagher announced during the Xbox Gamescom press conference. It's due out in holiday 2015. Gallagher didn't mention whether it was scheduled for Xbox 360, Xbox One or both.
Rise of the Tomb Raider is the sequel to Crystal Dynamics' 2013 reboot, Tomb Raider. The first trailer for Rise of the Tomb Raider shows Lara Croft in a therapist's office, anxious and unsettled over the horrific events of the first game, before she appears in a cave, bow in hand, and says, "We become who we're meant to be."
Update: Gallagher takes to Tumblr to explain the decision to make Rise of the Tomb Raider Xbox exclusive, noting that PlayStation and PC players will have Lara Croft and the Temple of Osiris. Read the important bits of his statement below.