That middleware exists: https://github.com/ValveSoftware/openvr
It supports both the Vive and the Rift, though I believe the Rift implementation is just a wrapper around Oculus' own SDK.
Since people are still figuring out what makes good VR and good paradigms for programming with VR, I think it'd be likely that any design by committee API would be a disaster
Re:A Third of Valve Is Now Working on VR
by macspoofing on Tuesday June 21, 2016 @08:05AM
(#11945052)
It wouldn't be the final word on VR API for all eternity. It's a starting point for the spec, which will change as the industry grows.
It doesn't matter much in practice - most people just use Unity or Unreal, which make it easy to target any major VR system. To the credit of these game engines, it's just not that hard to be compatible these days. That's why Oculus has started to use exclusivity contracts to gain an edge.
Would be nice if people had actually learned from that and rallied around a standard API/middleware for VR to start with, rather than trying to "console-ize" VR with hardware-specific exclusives. Maybe Valve/SteamVR will end up being that middleware?