Yes, there will be some wailing and gnashing of teeth, but the announcement explicitly outlines the reasons why the mechanics and features like the menagerie won’t be sticking around. In short, as much as the team (and players) enjoyed parts of the Bestiary experience, it’d create problems for new players and for keeping the menagerie updated, while demanding even more work to keep the crafting balanced. So it’s sad news if you had really hoped to keep the Bestiary League around in some form, but it seems like the best long-term health decision… even if it’ll be hard for the next league to be half as well-loved.
Source: Official Site; thanks to Pepperzine for the tip!