I imagine: Palpatine has Count Dooku contact the Sith, reveal that he’s one of them, and try to persuade them to join the confederacy since they have a common enemy in the form of the Republic.
- If they agree: the war proceeds as usual, probably taking a bit longer.
- If they disagree: Palpatine contacts the Sith as the chancellor of the Republic, and tells them that he’s one of them and that he’s already planning to wipe out the Jedi. He suggests that, instead of attacking, they come as refugees in order to increase public hatred for the Jedi.
- If they agree: the war proceeds as usual, perhaps ending a bit faster.
- If they disagree: The Sith, realizing that the war is staged, declare war on both the Republic and the Confederacy. Palpatine would have to completely redirect his plan, and manipulate the two factions into joining forces against the Sith army. This new crisis might still be enough to trick the galaxy into supporting the institution of a Galactic Empire, but it would be much harder to scapegoat the Jedi, so he would probably try to stop the Jedi from fighting in the war altogether. That way, because the Jedi and Sith aren’t publicly fighting one another, he can use propaganda to convince people they’re the same faction, and should all be destroyed.