I'm one of the Cycles 4D only customers, so this is a bummer.
I picked Cycles 4D up because it was really stable, had an affordable perpetual buy in, and loads of resources for learning from the Blender Cycles community. The only reason I found that this end of perpetual thing was happening was because I googled whether Cycles X was coming to Cycles 4D and stumbled upon this news. If they've communicated this with perpetual licence holders, I've missed it.
Anyway, I definitely won't be getting fused and will jump on another engine or move fully to Blender (where Cycles is much faster anyway). Not trying to turn this into a Blender vs C4D thread, but as someone who only does a small percentage of their client work in 3D, I'm finding it harder to justify these costs when Blender does so much of what I need (I still like using C4D more though).