If Rozemyne's group is actually going to come through the teleporter in the country gate, that's fantastic news for Letizia. Because that means that if the ship is leaving early, it'll run straight into the attack group and probably will be captured and turned back... or maybe, the strike group can even use the captured ship and the crew's silver clothes, to make an even more surprising surprise attack, since they can masquerade as Lanzenave reinforcement. Sure the deception will not last long, but it'll get them at least a little closer than flying in over the open ocean on their highbeasts.
But that's more of an expectation for the book as a whole. I expect that the prologue will be from Sylvester's POV and first show his negotiations with the royals, followed by a meeting with Eckhart and Justus. And once we've in Rozemyne's head again, I expect to fist get a chapter of preparations, with the actual attack only being launched in pre-pub part 2.