From the project own site :
OpenVX can be used directly by applications or accelerate linking of a higher level, for example, the popular open source open-source vision library [...]

... which seems completely understandable to me - you can use OpenVX directly or as OpenCV support.
However, it is also clear that OpenVX is currently vapourware - it exists only as a specification and a set of header files (without a real library).
A preliminary release of the specification allows developers and developers to provide feedback before the completion of the specification, which is expected within six months.
, - 19 2013 . , , , .
OpenVX GPU RPi, RPi, - .