Mercury stations Rx at 15 degrees Capricorn, on December 19th. It will be close to, but not exactly conjunct, Pluto in Capricorn. This suggests approaching a profound decision, or intense discovery. Mercury/Pluto, in authoritative Capricorn, is the word that no one argues with. The mind is made up, and there's no turning back, due to Pluto's complete transformation. Information/declarations penetrate the existing structure and embed themselves. Forever.
In light of this, Mercury's Rx will be the time to seriously (Capricorn) think it over, before you commit all your energy. Reviews, corrections and delays will have an official tone. There may be a tangle of rules to sort out, or the rules will be questioned. Going back may be part of your responsibilities. Since Mercury Rx can reintroduce someone from the past, traditions (another Capricorn theme) could be up for review.
The structure or status of an area in your life will be closely examined.
Mars will enter Pisces on December 19th as well, indicating that this review will align itself with a change of intent. You may shift your path entirely. Will it be permanent, or will it only last for the duration of this Rx? Time will tell. Mercury's Rx ingress into Sagittarius (January 4th) will take you all the way back to when the concept wasn't even solid. The adventure or ideal was exciting, but not proven. This review will be a deep one, designed to absolutely confirm something.
January 29th, 2017 will be significant, because Mercury will finally conjoin Pluto (17 degrees). This will be the conclusion, as the word/idea takes root and changes everything. As noted, it will be permanent, so use the Rx period to prepare. Interestingly, Mars will enter Aries on January 28th, continuing the alignment of action with information. But this time, the delays will be over and you'll be ready to start. Mars in Aries is pure action, and you'll have Mercury/Pluto's undeniable insight to back you up.
Check this post for a complete list of Mercury's aspects.