The verb is "to preempt". It has nothing to do with the word "empty." "To preempt" means to take something before other people do; or to become more important or prominent than something else. Your post refers to a big shopping day known as "Black Friday." "Black Friday" in the United States is a day when retailers (people and stores that sell directly to the public) sell their products at a big discount. However, now some retailers are beginning to offer great bargains on Thursday. They are trying to obtain customers on Thursday, before other retailers can try to sell things to the same people on Friday. They are trying to do on Thursday what used to be done on Black Friday, that is, sell products to consumers at a discount. Thus, they are trying to preempt Black Friday. Black Friday is the day after the American holiday Thanksgiving. Thanksgiving always falls on a Thursday. The traditional Thanksgiving meal is turkey. So, some stores now open their doors even before the turkey which is served on Thanksgiving becomes cold.