What would the end of the sentence be? It depends, for example: Next week is the start of November. Next week we'll celebrate her birthday. The event is next week. Our lesson is next week.

Hi, Jun. It depends on the context. You could say: "Next week is the last week of school." This is because you are referring to the week immediately after the current week. You could also say: "The next week that I am available to travel is in January." This is because you are specifying a week that is further in the future.