When S8 is out, the performance disparity between S6 and S8 will be massive. S8 users would not appreciate visual fidelity of a project built for S6, when S8 will be able to run much better visuals.
Oculus Store should be able to detect the phone model and provide apk built for a specific phone family (this way S6/S7 can have lower quality models and textures and S8 apk can have HD content). This would eliminate massive download size, which would be the thing when S6/S7/S8 assets all packed together.
Thanks beforehand !