Sushi, I have done three of the last four Bonnie mysteries. It is my understanding that this is a good time for Bonnie because she is taking some down time for the holidays and if there are any problems with the clues, Bonnie can fix them as opposed to being on the road and trying to do it.
Also, from reading mystery participants' comments, there are many who thank her for getting them through the holidays. They have no family or have lost loved ones and the mystery gives them something to occupy their time during the holidays.
Sewingitall, as others said, in mid October to late October, Bonnie announces the colors and the day after Thanksgiving, the first clue is given. Start checking her blog in October. I am on Facebook so I get her blog notices and anxiously wait for the colors and then that first clue. I never can keep up but that is okay with me. Finished making all the En Provence "pieces" in February, going to work on sewing the blocks together this summer.