Its completely in their interest considering how much visibility/publicity MS have gave this game. They're indie devs with a huge public presence, they must be very grateful towards MS with that, feeling they have a lot of confidence in their title.It's in no dev's best interest to be platform exclusive, but that doesn't stop platforms from having exclusives.
What you're saying basically amounts to platform begging, and unless I missed something it's against the rules on this forum.
This game will easily become as successful as Ori has been.