Answer
No, it is not in equilibrium during this brief moment.
Work Step by Step
At that moment, the force of gravity still acts on it. The net force on the ball is not zero and therefore is not in mechanical equilibrium.
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.