I would wholeheartedly OPPOSE replacing Firefly as not everyone who uses Poser seeks a "realistic" looking render. I have a camera for that and it's faster. However, if SM would like to add a second renderer that was PBR so that people could choose which they'd like to use, I'd be down with that.  

That would be my choice too.   Keep firefly but also add another renderer as an option.  As mentioned before, there are already free alternatives so it's time Poser had one too, at least the Pro version.