When does Midnight Season 1 end?

Currently we have no confirmation on when Midnight Season 1 will conclude. The most probable date is August 11.

Would I be able to get Mythic Keystone mounts after Season 1 ends?

It depend, however in most cases yes, you would be able to grab Calamitous Carrion and Convalescent Carrion with Timelost Saddle. However, exclusive top 1% mounts are only exclusive during the Season 1.

Would I be able to obtain Ashes of Belo'ren once Midnight Season 1 ends?

Yes, however the drop chance will be lowered significantly.

What is Ahead of the Curve (AotC), and why is it important?

Ahead of the Curve is a Feat of Strength achievement earned by defeating Dimensius on Heroic difficulty before Season 3 ends. Many raid groups require this achievement as proof of skill, making it valuable for future content.