All the above is premised on King fighting Zoro and giving him a #4 or #5 style battle. I don't actually consider those to be likely outcomes at this point, but if Oda does intend to pursue that path, I can't imagine how Oda would depict King as anything other than what would be considered a top tier (or at least, he'll show King to be above Marco).
More likely, Zoro wouldn't fight King or if he does, we get a battle in the style of #1 to #3. If King is revealed to indeed have a bounty significantly higher than Marco/Luffy and proceeds to defeat Marco, it would raise his standing enough that he isn't a massive underdog when he faces Zoro. Adding Awakening and (Advanced) COC would be enough to make him feel enough of a legitimate threat that a battle with Zoro would have actual tension in it again.
If I was to place any bets on what type of fight a potential Zoro vs King would be, I'd guess #2 (perhaps with some flavour of #3). Zoro has been heavily injured:
And I'm really sceptical that Oda will magic away those injuries. Oda didn't magic away:
- Zoro's injuries from his battle with Mihawk.
- It lasted until at least the end of Arlong Park.
- Zoro's injuries from taking all of Luffy's damage.
- It lasted until after Marineford.
History suggests that Oda doesn't magic away Zoro's injuries when there's a narrative purpose to them. Zoro may recover somewhat before his next fight(s), but he's unlikely to be fully healed.
Essentially, it's not that Oda can't heal Zoro, it's that narratively he wouldn't. Magicking away Zoro's damage means that Hakai had no consequences and Zoro's "sacrifice" was never actually a sacrifice at all.
Furthermore, Oda is loathe to pass on the opportunities to demonstrate Zoro shining even — no especially — in the face of adversity:
Defeating King while heavily injured could be the latest display of that.