If the seller dosn't have another offer come in by August. But not on bank owned properties.

It's highly doubtful.......selling the home as soon as possible will allow them to minimize their losses and move on.

Taking an initiative of extending the closing date will only serve to potentially deminish your chances of getting the property.

Lenders who own properties do not want to have to carry properties financially any longer than they have do.
Each month they continue to own a property, they lose money carrying and maintaining the property. So your chances of having a lender accept an offer with that long of a closing date are slim to none.