I think you’re right about the Facebook transition, especially with the design shifting to one more closely matching Facebook.

The dark horse, in my opinion, is spectrum.chat. It is fast, beautiful and being iterated on daily. It is also open source and open to feedback. The real time chat combines the best of discord and slack and the design is a step up from both of those and it.

It might not be a direct replacement to Reddit, but I think it could steal some traffic as it develops. Plus it is driven by a revenue model based on subscribers, not ads, sidestepping the current FB public relations issues.