I see this "fill a gap" phrase thrown out a lot. Classic WoW is not a gap filler, it is an entirely new game launch, akin to when any other recent Blizzard game has been launched, such as Overwatch. It is very likely that Blizzard advances Classic WoW into TBC, then WotLK, etc. It should be looked at as a game release that will be immensely popular for at MINIMUM 2 years, not as a Battle for Azeroth 4 month content gap filler