Eh.
Thrall’s “Story” was largely pre-WoW, and then just Cata + WoD.
It will likely conclude with him and Anduin getting married and getting over their collective self-doubt together.
(Jokes, but seriously, the inevitable outcome is just him getting over himself and being able to use the Elements again, and there’s likely not much for him to do after that. He’s not the central Horde figure anymore).
WoW isn’t one cohesive plot thread in general.
Vanilla was just setup and worldbuilding.
TBC was Blizzard flying by the seat of their pants following the rule of cool, which is why so much of it has been fiddled with in later expansions (mostly Legion and novels).
WotLK was the conclusion to WCIII but is largely a standalone thing within the context of WoW.
Cata set the new baseline and IMO was the beginning of a more continuous plotline. In that this is where Thrall handed off Warchief to Garrosh. Not much came of that just yet, but it’s the beginning.
MoP was all the result of that. Garrosh is Warchief, he’s on the warpath, it results in the whole Sha thing exploding, and culminates in the Siege of Orgrimmar.
WoD was the direct result of Garrosh escaping after that and working with Bronze Dragons or whatever.
Legion was the direct result of WoD happening (because AU Gul’dan came to MU Azeroth because of those events).
BfA was the direct result of the end of Legion (Resource War stemming from Sargeras stabbing Azeroth).
Shadowlands is loosely linked by Sylvanas being ousted at the end of BfA and her being the one to break the veil or whatever, but frankly it was mostly it’s own thing and it probably didn’t need to be her, nor did the timing have to be after BfA’s events.
Dragonflight and the next 3 expansions will be the next big plotline. Dragonflight directly leads into the Worldsoul Saga thanks to Iridiwhatever and the Dark Heart + Xally.
So…
Vanilla → WotLK: Standalone Plots utilizing known locations and characters from the RTS
Cata → BfA: Legion-Centric Plot triggered by Garrosh due to Thrall’s lack of Foresight.
Shadowlands: Standalone Plot
Dragonflight → Worldsoul Saga: 2nd continuous plotline, we’ll see where it goes.