I'd rather they just revamped EK and Kalimdor and brought them into 2019. Entirely new versions of the 2 seems overly complicated.
We already experienced a WoW 2.0 of sorts with Legion. It set the bar for the game never before seen, not even during MoP which we know had a change in design philosophies. Then WoD came with its intention of never giving us more than 6.2 and set them back quite badly in goodwill.
Then again, another revamp of EK and Kalimdor couldn't be done as they did the Cata revamp. They still reused just about all the art assets from each zone for the revamp, meaning those zones still have vanilla models and textures on trees and ground clutter. With a new revamp, they'd also need to 100% visually update every mob, every critter, every piece of foliage, ground textures, make use of new light, fog etc.
So when thinking that far, it doesn't seem too far fetched with a total revamp whilst saving Cata EK/Kalimdor as "timewalking"-type leveling content.
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They seem to believe that WoD was cut short, and hope that since they're not enjoying BFA, noone is. Ergo Blizzard should "cut their losses" and focus on 9.0.
But that's not what happened, we had an interview linked in this very thread where one of the leads coming back to WoW during WoD was concerned to learn that they didn't plan for more content beyond Tanaan. It was a hack job of an expansion all the way through, minimum effort.
Legion had 3 major patches, BfA will have 3 major patches, and bringing out .5 patches also gives them more time to work on 9.0 than if they'd just cut and run like the crowd of naysay crusaders suggest.