We'll disagree on our projections

You might be right! But the way Oda combines a lot of different things into a single arc has me feeling like:
-Reverie will happen during the Wano / Kaidou arc; Luffy's first 1v1 fight with a Yonkou and winning.
-Final arc with Shanks & Blackbeard for One Piece and after left. Pretty sure while Luffy will fight Shanks that it's gonna be like Luffy v Blackbeard for final boss of the series and then Luffy v Shanks for epilogue final "fight" in a Luffy v Usopp way. It's just been foreshadowed setup so much and it's so perfect for Luffy v Blackbeard -> friendly Luffy v Shanks fight where Luffy surpasses Shanks and Shanks sees him off with a smile as he gets One Piece and becomes the pirate king.
They could do another arc after OP, but then it could go on forever and I think Oda will end it on Luffy v Shanks -> Luffy gets One Piece -> THE.END (all within like 1-2 chapters at the conclusion of Luffy v Shanks fight) and anything else would be a sequel series/spin-off later.
At the end of the day there's only 2 real enemies left that are stronger than Luffy: Kaidou and Blackbeard. Each arc needs a major antagonist and there's 2 left. I don't see more than 2 arcs before OP ends. But that's all just my guess.