I suspect that the original Zenos will play the part of the final fight of 4.5. I doubt very much that he'll regain his body from Elidibus. We've seen Elidibus scheme from the shadows as far back as 2.0 and it's only recently that he has made a direct move. I don't see that advantage ending immediately. If anyone is to be a thorn in his side I suspect it'll be Varis given that he doesn't appear to be fully on board with what Elidibus has been doing. Though given that the corpse that Elidibus is piloting is the heir to the throne of Garlemald, he has something of an advantage when it comes to blackmailing the Emperor.