The impression I've got is that the expansions in the Saga will be perhaps lighter on the features, but also shorter and - hopefully - cutting out the expansion-end content draught completely. Keeping the current content cadence (so about one major patch every half a year) and two major patches per expansion would give us one expansion every 1.5 year, so the Saga would in theory provide us 4.5 years of regular updates with a Dragonflight cadence and no breaks inbetween. Next expansion coming out whenever you would expect a new major patch. Sounds kinda good.
Unfortunately it probably means that we are 5 years away from the full world revamp. But after these 5 years and ending the "Warcraft Storyline"... where do we even go from there? Most stories in the game are connected to the Saga. I can only imagine we will get a much longer time-skip, with the world moving 20 or 50 years ahead, and revamp will be based on the new status quo. A soft reboot of sorts, allowing new players to enter the game without knowing the last 30 years of lore and not feel completely lost. And only from there a new storylines will start to emerge.