I am pretty shure that it went the other way around, that it were the Keyshot people who contacted Pixologic.
So if someone wants the render engine they like to be added to ZBrush 5, all they have to do is convince the company that creates it to code a bridge that integrates as perfectly as Keyshot does.
I am absolutely shure Pixologic would not mind bridges to, say, VRay, Arnold, Indigo, Maxwell and Marmoset.
The more, the merrier.