I have been getting notifications about the new Team GO Rocket research for December but have not gotten the special research itself. I was wondering if anybody here has gotten it or if the notification has gone out before the research was actually available? I have a feeling that I may need to finish the previous research task Looming in the Shadows but it also is a pretty Niantic move to push the notification out too early...
Yes, you need to finish Looming in the Shadows to get the next research task, A Challenging Development.
The quests in this series are actually identical. Every month, if you have completed the previous quest, you get the new one. The most important reward from the quest is the ability to fight Giovanni and get a shadow legendary Pokemon. Each quest lets you get one of those Pokemon, and the Pokemon you get depends on what month it is when you do the fight.