No one can know what's going to happen in the future.
Literal
Future [in-に] what [subject-が] happen [question-か] know thing [topic-は] cannot-do.
A textbook example of an embedded question with か-nominalization: 何が起こるか ('what will happen') becomes a noun phrase serving as the object of 知る. Then ことはできない ('cannot do the thing of X') is the formal inability pattern, an alternative to the potential form 知れない.