I think most people agree on that. Kaido and Big Mom’s plotlines will end earlier in the story.
Shanks and Blackbeard’s plotlines are being saved up closer to be the End of the Series material and are tied a lot closer to Luffy’s personal dreams and goals and also seem to be tied more closely to the World Government and Roger/One Piece plotlines.
There is a lot of symbolism between Luffy/Blackbeard/Shanks and how all of their crews are almost build to be counters of each other. How Shanks is the reason Luffy started his journey and career and his biggest inspiration to become Pirate.
How Blackbeard and Shanks have history and Shanks was pretty much the only guy taking him seriously from the very start of the story and saw his danger.
How Blackbeard was basically introduced an opposite of Luffy and had a similar progression throughout the storyline as the main character had (as opposed to Big Mom and Kaido who are at the same spot where they started the story as Yonkos pretty much) and also how Blackbeard is pretty much considered to be the main competition Luffy has for Pirate King.
It would be interesting to see the match-ups between those crews. Would be cool if we had all three fighting between each other at some point, like Straw hat Pirates vs Red Hair Pirates in a tone of rivalry, then Blackbeard Pirates vs Red Hair Pirates and finally Blackbeard Pirates vs Straw Hat Pirates.
*Theory by Dr_Dankology