Sorry, you're right - it was announced the next year but took several more years to release. (I believe that was said at Blizzcon '16 based on eg. https://www.reddit.com/r/gaming/comments/4dqtvj/you_think_yo... and WoW Classic was announced at Blizzcon '17 https://diaryofdennis.com/2017/11/04/official-vanilla-world-...)