Damn it Mario, I was trying to type all of this and then you came along… ![:laughing: 😆](https://forums.arlongpark.net/assets/plugins/nodebb-plugin-emoji/emoji/android/1f606.png?v=i9pjs0vqrag)
Nevertheless, here's my take (basically the same as yours)…
There's another thing I've had in mind for some time now:
Luffy will meet Shanks at Elbaf.
Some arguments for this:
1. The meeting between Shanks and Luffy has been promised since Chapter 1. Probably without the "Giving-back-the-hat"-thing, but Shanks serves as the inspiration for Luffy and without him there wouldn't be any journey. And reunion with him that was promised since Chapter 1? I think we can safely assume it will take place. It MUST take place.
2. Shanks said Luffy should give him back the hat when he's a great pirate. Again, the hat is such an integral part of Luffy's character that I doubt he'll give him back (or that Shanks would even accept Luffy's request if he would do so), but I think we're all agree pretty much that this foreshadows, again, an actual meeting. Simply, they'll both should see each other at least one time before the story ends.
3. What better way to show that Luffy is a great pirate and quasi on Shanks level than after he overcame a Yonko? So the meeting should take place after Kaido's been defeated.
4. If the arc-sequence will be Totland-Reverie-Wano-Elbaf-Raftel (there has been much discussion and arguments in favor of all this), this leaves only Elbaf as the last place between Wano and the Endgame (starting with Raftel).
5. Shouldn't Luffy meet Shanks at least BEFORE he's been on Raftel when all the secrets are revealed? Shank's line to him in Chapter one mentions when Luffy's "a great pirate" and not when he's pirate king. To be pirate king, he must reach Raftel. To be only a great pirate and "fulfill" Shanks (and thus Oda's) requirement for another meeting, defeating a Yonko would be sufficient
6. We'll likely get a flashback with Oden and the Roger Pirates at Wano. Which should include Shanks also, since he obviously was a cabin boy there. So we would have Shanks character set up a little bit already in Wano. Elbaf would be the rgiht moment to have the meeting and reveal more of him (Oda also shows Shanks suspiciously rarely even though he has such a huge impact on the overall story… He only appears in really important moments).
7. The big theory (and the elephant in the room) of course is, that Shanks will be killed by Blackbeard. I mean we need to see him a little bit BEFORE that. And I would argue that Shanks being killed by the final villain Blackbeard and the discovery of One Piece by Luffy would be something which should nicely coincide. So we need to see more of shanks before we're at raftel, at which point he'll likely already will have met his demise. Elbaf fits.
8. And if Greg's speculation is right, Blackbeard could show up at Elbaf and destroy the tree of life. And than we would already have a nice set-up fore the Shanks vs Blackbeard fight, while the Strawhats set sail to raftel. Shanks could also act as some kind of protector, to ensure that Luffy and the others will reach Raftel unharmed while he's trying to hold Teach back.
Edit post:
9. Elbaf has some kind of Viking/Nordic-theme. And Oda himself has said that he was very much influenced by this series (his affection towards pirates), directed by Hiraoshi Saito:
https://en.wikipedia.org/wiki/Vicky_the_Viking
Like Wano, where Oda probably will include numerous refernces to Japanese folklore and culture for obvious reasons, Elbaf could be some kind of "Homage"-arc to this series, which inspired him. Expect Elbaf to be enormous in story importance.
Also Shanks ship has a Viking-theme. Maybe another clue?
10. I like the theory that besides Blackbeard, sakazuki's marines, which were shown to be much more ferocious than before the time-skip, will take out a Yonko too. I mean Sakazuki relocated the Marine-HQ to the New World. Why would Oda include such a hint if there wouldn't be a confrontation between the Yonko and the Marines at some point? So Kaido is taken out by Luffy (and others), Shanks by Blackbeard… Leaves Big Mom, which would be nice to be taken out by Sakazuki.
11. This would nicely mirror the end of the first half of the Grand Line, when at Marineford, two important pirates who were friendly/affectionate towards Luffy, were taken out by Sakazuki and Blackbeard: Ace and Whitebeard.
Sakazuki and Teach will do this again, when they take out Linlin and Shanks. Their actions also, in a strange way, seem to benefit each other... (Sakazuki weakened Newgate, Blackbeards crew was able to finfish him off. Blackbeard captured Bonney, who then fell into sakazuki's hands)
Altogether,all of this may not be the most difficult thing to theorize given the author's habits and foreshadowing, so I'm not claiming that I reinvented the wheel here. But still, I think this is a likely sequence of events...