In an interview with GameSpot, Game Director Ion Hazzikostas talked about a possible old-world update as WoW is reaching its 20th anniversary.
Full GameSpot Interview
When asked about if the 20th anniversary would be an opportune time to revamp Kalimdor and Eastern Kingdoms, Ion mentions that a revamp is something «likely to happen» in the future, but with no timeline for it set in stone. However, the team learned many lessons from Cataclysm and would have ways to allow players to return to old versions of zones if that would ever happen.