This question is very similar to the often asked "Do we need to read the Agile Practice Guide for the PMP Exam?". Here is what PMI said about the Practice Guide, and pretty much the same answer also applies to the trends and emerging practices:
"The Agile Practice Guide offers a more comprehensive perspective on agile applications and is a useful resource for gaining a greater understanding of this approach to project management. In-depth knowledge of agile practices is not required for the PMP®, though. There could be some agile questions on the PMP exam as we know the practice of agile methods is growing in prominence and project managers need to be equipped to choose the most appropriate approach for their projects. However, any agile related questions would still need to fit within the context of the current PMP exam content outline. That being the case, people should not expect to see in-depth assessment of agile topics on the PMP exam.”
So same with trends and emerging practices. Expect to be asked, but don' t expect too many in-depth questions.