For Mac Rhino that market is wide open. Besides native Cycles for Rhino and as far as I know there is only Maxwell V5 ( still not fully developed last time I read about it) as an integrated plugin for Rhino. And then you have Keyshot( super expensive and industrial design oriented) and Twinmotion connected via live links but not integrated within Rhino. Also, Chaos seems to show not interest in developing Vray for Mac rhino.
As a long time Maxwell Render user, I no longer use it as I lost confidence on the company, I’m pretty sure that Jeremy will not disappoint us with his top notch support and commitment to develop the tightest integrated plugin for Rhino. But I agree with you that is not going to be easy for them to gain that market as Bella is still very young and the quality is not the only or most important aspect of a render engine nowadays.
If you are listening Jeremy, please focus on an intuitive and easy to use tool with very good assets, at least that’s what I look for when searching for a render engine this days.