Some of the changes in the new Formats are minimal and there are many things that have not changed at all. However, there are many changes that are significant and these should be studied carefully. BANA has not yet announced an implementation date. And it is standard practice not to change rules in the middle of a current transcription.
The new guidelines have been released and posted. This means that transcribers are authorized to use these new guidelines for any new book that is started. If there is a new book to do and further study of the new formats is needed, go right ahead and transcribe that book under the old formats. You should take all the transition time you need. At some point BANA will announceme an implementation date, usually in 6 months or a year from the present and that means that BY THAT DATE, new books should be done with the new guidelines.
To summarize, use the new guidelines as soon as you feel ready. You MUST uas the new guidelines for any new book after the implementation date.