First off, WoD did not have us travel in time; it had us travel to an alternate timeline.
Second the main issue with WoD was not at all the story. It was the lack of non-raiding endgame mostly because of the lack of a reward system like Valor to prop up dungeons and other activities; early Apexis gear just sucked. This made the random loot from the garrison the only progression for much of the playerbase. The lack of further content after launch (because of WoD being a disaster in development due to Garrison tech not playing nice, constantly scaling back on original promises, releasing with an unfinished zone in Gorgrond that was effectively patched up with rares and zone objectives) doomed it and Tanaan's return to form could just not save it.
The story itself was mostly inoffensive; the main issue was that it was extremely low stakes. We went there to stop the Iron Horde invasion and we very much did that in the first 30 minutes of playtime by destroying their Dark Portal. We were clearly NOT stranded there since we could portal in supplies IN LORE during the questing experience. Why we stayed after, who knows. The Iron Horde never managed to be much of a threat to us regardless and I at least felt we were more there to help the AU Draenei/Frostwolves than ourselves. Still I found the only problematic parts to be the ONE LEGION bullshit and the "Draenor is Free" insanity because devs jerk off to Grom even though he paved roads with draenei baby skulls even without the fel excuse. . .
In fact we had far more offensive time travel in WoW long before WoD; Well of Eternity as a dungeon is a massive plot hole where we go back in time in our OWN timeline, steal the demon soul and thus completely change the course of history which is somehow ignored.
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I expect Avaloren and yet am not sure about it. DF was supposed to have the MoP feel but imo it has failed at that by poorly integrating DF lore to Azeroth's history; with MoP everything was new yet somehow managed to feel connected to the rest of WoW. Yet Avaloren is exactly the same theme; explore a completely new continent with different races and people. Would they do the same thing twice in a row?
If we get Avaloren I expect a void influenced society, plenty of Titan and Black Empire architecture, an important Titan Facility that acts as the expansion's McGuffin (Odyn's group had the Ulduar and the Forge of Wills, Ra's had Uldum and the Forge of Origination, Innaria's will have Uldorus and the Forge of ?); possibly the Titan endgame facility that is meant to help Azeroth be born.
I don't see that as a South Seas expansion though, more of a new continent, possibly with areas that are locked from exploration early on and unlocked as the expansion advances. Avaloren should not be in the South Seas anyway (since if it was, it would have been part of the Kalimdor landmass; it should be at the other side of the planet.
It is the concept that is more heavily hinted at for sure though.
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My preference is very much World Revamp with part of the Revamp being the current content and a new Evergreen system of events that provide a secondary focus to past expansion or/and a revamped area that occurs every season. My preference if it has to be entirely new content would be a Hollow World concept with a massive Titan Facility around the World soul adjoining to multiple underground zones and access points all over the planet. Could include Azjol'Nerub, a massive silithid hive area under Silithus, a sunless sea zone, the Blingtron War, the dwarven civilization mentioned in the Uldaman books etc.