This popped up on the BJCP Home Page and clarifies what to actually study for future exams.
Style Guidance for Future Exams
The Exam Directors have decided that the scope of future exams using the 2015 BJCP Style Guidelines will be beer style categories 1 through 26. Categories 27 (historical beer) through 34 (specialty beer) will not be covered on any exam. More guidance will be provided when the online question pool is complete, the written exam questions are updated, and guidance for tasting exam administrators is finished. All mead and cider styles are covered on the exams with the exclusion of the final specialty-type styles (M4B Historical Mead, M4C Experimental Mead, C2F Specialty Cider/Perry). This information is forward-looking, and applies to exams after the 2015 Guideline cutover in November, not exams currently given.
Hopefully that information will help as you prep for exams in the future.