Square Enix confirms: "Rise of the Tomb Raider exclusivity does have a duration but we aren't [allowed] discussing those details at this time"

[JustBeingReal]

It's not like Microsoft saved Rise of the Tomb Raider from going to the graveyard, it's only launching first on XBox One and 360 next holiday, so it'll probably be out on PS4, PC and PS3 within a few months after that.

PC and Playstation have a long standing history with the franchise, it's like saying Final Fantasy could be an exclusive on Xbox, it would destroy SE's reputation if they don't at least release the game on PS4 and PC.
PS3 is a huge audience to ignore as well consider the game sold more on that platform than anywhere else.