After stepping into the realm of the life afterlife, game players are presented to the Maw, a location that is used in WoTLK Gold finale. While certain events force players to leave the Maw upon first arriving in WotLK Classic, they'll be brought back to the area by expansion's end. Famously, Arthas Menethil was brought into the Maw following his demise as Lich King over a decade earlier. Due to this, many fans speculated that Arthas could be in the forthcoming WoW: WotLK Classic expansion.

The Maw mostly serves as WotLK Classic' endgame content, so it's natural that WoW's Arthas Menethil is going to be included. The majority of this could relate to Sylvanas who died by Arthas at the time of Warcraft 3 before Arthas resurrected her. Because Sylvanas is such a significant role in WoW: WotLK Classic with such an extensive relationship with Arthas so it makes sense he'll show up in the future.

Just before the start of the content that will be ending in WotLK Classic, Sylvanas discloses her plans to change how the afterlife is arranged. While her motivations aren't fully explained (Sylvanas is Sylvanas at the end of the day) the revelation certainly opens the way for players and Sylvanas to meet World of Warcraft's Arthas Menethil again. It's reasonable to assume Arthas will be revealed at some point when it comes to WotLK Classic, even if that's in a future update after launch.

A character with a cult following like Arthas Menethil will surely appear in the expansion at some point. He's already been taken into the maw which makes sense that players could run upon him in the Maw. However, it's possible that his appearance is reserved for the later sequence of events in the game since it would be a big event to reveal. If Arthas isn't in World of Warcraft: buy WoTLK Gold will be a massive missed chance. The chances are good, however that he'll show to the game at some point.