I would trust this doesn't mean Firefly development has stopped. PBRs are nice and all, but for a lot of applications are not necessary.

This is exactly why FireFly is staying. there are also some things it does  better. This emphasizes that you need a choice in render engines. Now you will have another.

I would note this doesn't actually answer the question I was implying, so perhaps I should ask it straight: are there going to be improvements/changes to Firefly or has development on it been essentially frozen?