When will my waitlist slot get confirmed?

Waitlist slots are given preference as and when there is a cancellation.

There is no definite time in which your waitlist slot can get confirmed.
If there is a cancellation immediately after you register on waitlist, you will be moved to the main batch and a mail will be sent, asking you to finish the payment.

There might be no cancellation in the batch and you might never get a chance to register as well.