Well, we're kind of running out of places to visit. So, if the Emerald City is actually going to be important, it can probably only be either Lodestar or Laugh Tale, itself. MAYBE it could be a Sky Island, or on the Moon? But those two main locations feel more likely to me.
Personally, originally, I thought that Elbaph was going to be our Emerald City. We knew trees were important to Elbaph, due to the Adam Wood. Trees are green. BOOM, done! But...no, it looks like it isn't.
And, at this point? I might actually be leaning towards Laugh Tale being our Emerald City. We now know for a fact that Joyboy left a message there. Which would make Joyboy our "Great and Powerful Oz" figure. And it does kind of feel fitting for our ultimate destination to be this former gleaming city on a hill, as it were. Plus, if Laugh Tale is somehow connected to the origin of Devil Fruits, and other powers in this world, it would kind of make sense for Laugh Tale to be inspired by a literal "dream world", like Oz, where anything can happen.
Plus, it's worth mentioning, the Emerald City could have some connection to the Ancient Giants. Because, the name "Oars" can also be translated as "Oz". If you can track down some old fan translations from back in the day, they even called "Oars" "Oz" back then. So, there could be some connection there. Whether that makes Lodestar or Laugh Tale the more likely candidate for our Emerald City is still up in the air.
So, I don't know. Lodestar is definitely still a possibility. I could see it happening. But, Laugh Tale itself feels like it could shape up for a better "Oz" analogue in this story. We'll see.