Blizzard has stated that there is no immediate need for a World of Warcraft 2 as the MMO has been rebuilt multiple times.
World of Warcraft is considered a 'ship of Theseus of video games', with every piece of it recreated and rebuilt over time.
The WoW team may have overloaded players with too many special events, leading to feedback that it feels like too much to ask on top of existing content.
The feedback from players has made the WoW team realize the potential strain of additional content on top of existing gameplay.