"like there was no tomorrow" is an expression which means doing as much as you can in as short a time as possible, sometimes recklessly and carelessly. If the world were to literally end tomorrow, you would want to do as much as you can today. A store "offering upgrades like there there is no tomorrow" means they want to upgrade as many phones as they can very quickly. There are probably really good deals - the idea is to get a lot of quick sales.

在大楼的一层，曾经是Pliskin的杂货店的地方，开了一家一元店，紧挨着它的，不是那位修鞋匠，而是一家手机零售店，人们疯狂的抢购新机，好像明天就是世界末日了一般。