to wait for the other shoe to drop字面意思是等另一只鞋子掉下来，引申为等待最后的（坏）结果、提心吊胆地等待最后的结果。

【例句】
At the hearings they haven't dug yet into this man's personal background. But there are rumors he has some shady things in his past, so everybody's waiting for the other shoe to drop.
在这些听证会上，他们到目前为止还没有去追究这人以往生活方面的情况。但是，有传说讲他过去有些不光彩的事，所以每个人都在等待最后的结局。

To wait for the next, seemingly unavoidable thing to happen. This phrase often has a negative connotation.
等待下一个似乎不可避免的事情发生。这个短语通常有消极的含义。