There will shortly be a statement regarding which PrCs have CDQs required, recommended or completely optional. We know there has been some confusion in this matter. We're finishing up the discussion and it will be posted probably within a few days.
However, a character development thread is pretty a good idea for any new classes one wants to add, and especially for PrCs. It's quite likely that a PrC request would be denied without a CD thread showing progress toward that particular class.