We did this at FLL some years ago. Our family of four got bumped off three consecutive flights for our return to SAN after spring break. Mopped up $6000 in AA vouchers. It was magic. But I have not heard of this happening recently. I think gate agents look at the next flight, see that it is already oversold, and keep going until they find one with seats available. If you are not willing to wait until the next available flight, they probably will not use your seat and will not issue the bump to you. Instead, they'd probably resort to involuntary bumping, despite all the unpleasant side effects that go along with that.