While Blizzard has been very dismissive of any question about the future of Dragonflight beyond Season 3, there might be something in the data indicating an upcoming Season 4.
They’ve done it before with Patch 9.2 when they added both Season 3 and Season 4 Vicious Saddle mounts in a PTR build. Originally neither mount had a source listed, but later on, we found out that the Croaker was the Season 3 reward and the Wolf the Season 4 reward.