Blizzard made some updates to Kalimdor Cup. The event is now available to players at Level 30 and you don’t have to own Dragonflight to participate in the event.

(Source)

Hey folks! We’ve made some changes to the availability of the Kalimdor Cup. Players level 30 and above will now have access to the races, intro quest, and rewards vendor. This availability now extends to players that don’t own Dragonflight or have not yet learned dragonriding. We’ve also added Lord Andestrasz and crew to Stormwind and Orgrimmar for convenience. In Stormwind, they can be found on top of the northwestern tunnel out of the Trade District. In Orgrimmar, they are located by the northern zeppelin tower. Happy flying!