Is Uncorrupted Voidwing Still Available?

Can you get uncorrupted Voidwing?

Reward from completing the quest Lost Flight given by Spawn of Vexiona. Item is lootable from N'Zoth, the Corruptor in Ny'alotha, the Waking City on Heroic difficulty or higher.

Is the uncorrupted Voidwing available until Shadowlands launches or is it gone now?

While Ahead of the Curve: N'Zoth the Corruptor will be gone in 9.0, you can still obtain Uncorrupted Voidwing until Shadowlands launches. When killing Heroic: N'zoth you will receive Spawn of Vexiona, that starts the quest Lost Flight, which rewards Uncorrupted Voidwing.