Before everyone jumps on their Keyboards with rapid typing speeds, please read this out first. I am going to make this as simple and as short as possible.
TLDR - This poster single handely guessed every expansion/theme and realized what tha patterns are of the storyline/story arcs way before BFA or Shadowlands was even a thing and was absolutely on the dot. This was post was published on September 24th, 2017 which is roughly 1 month and a half before BFA's Reveal/Announcement at Blizzcon that year. The full post is translated from chinese to english down below.
TLDR #2
1 - He predicted that 8.0 is about ancient god line (Old Gods/N'Zoth) and is related to WotLK
2 - Then he precited that 9.0 takes place in the Shadow kingdom or as we know it Shadowlands and is is corresponding to the happenings in WotLK and that the content talks about a new Lich King which in this case as we know it Bolvar.
3 - Both 10.0 and 11.0 will be Dragon and Elemental related and both of these elements will conclude.
4 - 12.0 Will follow up to Mists of Panderia warfare between Horde and the Alliances, basically another war of sort and there will be another shake up with the leadership.
5 - 13.0 is where the fight/confront the Void Lord who's story was being built up for a while now.
Source - https://bbs.nga.cn/read.php?tid=12510507
On the chinese Website above, a user posted the following (I am not chinese, using Google translator here)
Today, when reviewing the content of each expansion piece of wow, I suddenly discovered a fact: the content of the expansion piece of tbc is actually divided into two parts, the Draenor line and the Burning Legion line, corresponding to the content of wod and leg respectively.
That is to say, the two expansion pieces 6.0 and 7.0 are split from the expansion piece 2.0. From this, we continue to speculate that 8.0 should be the ancient god line corresponding to WotlK, and 9.0 should correspond to the natural disaster line of WotLK, and the content should be the content of the new Lich King and the Kingdom of Shadows.
10.0 and 11.0 correspond to the dragon line and element line of ctm, and the story of dragon and element lord will end.
12.0 corresponds to mop's alliance and tribal war lines. It is speculated that the current major cities and faction leaders will usher in the last major reshuffle.
13.0 corresponds to the Sha line of mop, but this time the protagonist will be wow's final boss Void Lord.
Among them, in 8.0~12.0, the Void forces will appear frequently, and they are also the mastermind behind these expansions.
The Burning Legion debuted in 2.0, and after four expansions from 3.0 to 6.0, it came to an end in 7.0.
The Void Force debuted in 7.0, and after four expansions from 8.0 to 12.0, it finally came to an end in 13.0.