Cygnuses are unavailable.

Considering that everyone knows about the dream, four of the five heroes and a replacement for the one that died are here, the Resistance is around, etc., as soon as Ereve falls from the sky and lands near Henesys, everyone will launch a massive invasion.

So no, unless the Black Mage is planning on exactly that (I don't think Wizet's writing staff is that clever.), we're not going to see Arkarium's false future of Cygnus getting killed by the heroes play out.