Warcraft lost the fun when it became a world.
I'm curious as to how Blizzard plans to just separate the lore of the most played MMORPG. In Wrath of the Lich King, Arthas died, which resulted in the annihilation of an entire race, I'm not sure if anyone's going to treat it lightly if Blizzard just decides that it did happen, but then again, if they decide that it didn't happen, what are we playing in WoW, some kind of myth, some kind of dream? It would kind of ruin the feeling for them.
I would like to see RTS WarCraft history somewhat meshed with WoW lore, I liked the concepts of Scarlet Crusade and the Argent Dawn. But I would not mind at all if they ditched the Lich King's death.