Mihawk is definitely not EoS material and its definitely not safe to say anything about his power level .
It's safe to say the Strongest Swordsman is indeed the Strongest Swordsman. Trying to look for alternatives is the unsafe option. But let's try and break this down.
1. Zoro has said he wants to be the greatest swordsman ever. In other words, better than all swordsman past and present. This means Zoro will surpass Oden even though he's dead.
2. Zoro is being given Oden's blade which he scarred Kaido with. Zoro and Oden are now being directly measured. For Zoro to prove he's surpassed Oden, he'd have to match or surpass Oden's feat. Otherwise, there would be no way of truly proving Zoro has surpassed Oden. Thus, Zoro's "Strongest Swordsman ever" claim rings hollow.
3. If Zoro does just that, it means he's either equal or greater than Oden at that point.
4. Mihawk is the current WSS, so he must be defeated in combat.
5. Defeating Mihawk or defeating someone else who defeated Mihawk beforehand is a step that comes after surpassing Oden's cutting feat.
6. Strawhats typically get stronger after every arc.
7. Depending on how many arcs come after before Zoro fight with Mihawk or other, he'll have been a certain amount stronger than the point he was after the Oden cutting feat.
8. A key fight like determining the Strongest Swordsman wouldn't be anything less than a high diff
9. In short, Mihawk or whoever Zoro faces at that stage would reasonably be stronger than Oden, as they will fight a stronger Zoro than the one that came off his Oden cutting feat.