Replying to another thread about what class could be next got me thinking about what sorts of aces Blizzard still has in the hole. So, without devolving into an argument about what some might find fun and others wouldn't, what are some of the things we at MMO-Champion feel Blizzard can still offer in future expansions to draw players?
Zones - We're going to Argus in this expansion, at least briefly. That said, they aren't above taking us out of Azeroth every few years. The chance to explore other worlds in the Warcraft universe remains a point of intrigue to some and can pave the way for expansions to come. Similarly, there are still many zones in lore that have yet to be explored fully on Azeroth proper. Kul'tiras, old god/Azshara territory, and Zandalar (raised from the sea or otherwise) spring to mind.
Races - Say what you want about races, but they're a big draw in a given expansion. Players as a whole enjoy seeing the game from fresh perspectives. Frequently requested races include ogres, naga, and the myriad of sub-races seen in game already. More recent requests have been tailored to include Jinyu, Saberon, and the plant race found in Draenor. The common belief is, if it can be a follower, it can be a playable race.
Classes - Blizzard has stated that they will eventually run out of new classes to offer (presumably before races), but they have so far managed to offer a new class every other expansion since Wrath of the Lich King. They have also offered new class combinations in Burning Crusade (shaman/paladin to opposite factions), Cataclysm (many), and Legion (gnome hunters). With the last, they even added additional gameplay options that previously didn't exist, which may help to show where things could go for the future. Finally, while they haven't capitalized on it yet, adding new specs (a'la druid) is still on the table. Giving warriors gladiator back is one possibility that is particularly dear to me. We'll know for sure when they announce expansion 8, since the chances of getting any of these (except race/class combos) in x7 are slim-to-none.
Gameplay - This one is a bit of everything above and other. New ways to experience classes, like hunters getting mechanical pets in Legion; races, like worgen with a racial mount form; or zones like east suramar's underwater area, which is a definite upgrade from Cata's underwater zones. Gameplay also includes things like new fight mechanics (mounted/flying), minigames (pet battles, brawler's guild), professions, and class hall equivalents.
What are some of the things that would draw (not dissuade) you to a new expansion? Anything besides these 4 that I may have not thought of?