Fractal just released Dyna-Cabs, and already said additional cabs were in the queue. Cliff said they take a lot of work, so perhaps that's keeping him busy.
I think if Fractal was going to shelve development of the FX3, they'd be up-front about it and say so. Their past behavior was to continue supporting units after they'd announced a replacement, so why would they change now?
After looking at the firmware releases for the FX3 here's a little summary starting from March 14, 2018 to date:
View attachment 126029
If other companies had that sort of responsiveness their customers would be ecstatic, but here? This sort of question… sigh.