The trial is set to last two weeks.

审判可能要持续两个星期。(可以把is set to last理解为句子谓语，last为动词）

be set to do sth可能要做某事

以上结构类似于“be likely to do ; be supposed to do ,be inclined to do sth”

set  adj.做好准备的;可能的(英文解释： If you are set to do something, you are ready to do it or are likely to do it. If something is set to happen, it is about to happen or likely to happen）

Roberto Baggio was set to become one of the greatest players of all time.

罗伯特·巴乔注定会成为迄今为止最伟大的球员之一。

The talks are set to continue through the week.

谈判可能会持续一周。