By developing using the
OSVR API, they should be able to secure compatibility with all VR headsets in the long run. Valve has already officially said that they're supporting plugin development for OSVR compatibility (so OSVR game devs don't have to do anything to be compatible with the Vive). As of now I don't think that there is a plugin for CV1 support yet, but in the future there definitely will be (thanks to the open source community).
So if they stick to OSVR now, the game will easily gain support for future HMDs without having to code it in. The OSVR runtime will update independently on users' systems, and will be compatible, guaranteed, with any new HMD that hits the market, whether its built for OpenVR or OSVR (and possibly Oculus in the future at some point).
And don't forget this $399.99 beauty that was just very recently announced from Razer. Seems like it can rival the Rift CV1 in terms of display resolution. No reviews yet, but seems like a steal at that price.
EDIT: Also, OSVR does support the DK2 and DK1.