Personally I think we have one more island before the conflict (Elbaf being for the Burned Scar Man or something else), but I pretty much agree with your layout at least, regardless of how or where it happens lol.
The reason I think this is because Blackbeard is about to find out about Pluton, which is decently close by. If Oda wants him to take advantage and force Wano to open its borders, we realistically need at least one more arc to act a buffer.
We'll see though.