Tonight at Time To Play Mag's Holiday Showcase in New York, a Sixth Ranger Key Pack (I am dubbing Super Megaforce Set C) was seen. Images were posted by PrimeTimeParent, Peekababy and momconfessionals on Instagram. Thanks to Ranger Report and Razzle1337 for the info.
It looks like it comes with Super Megaforce Silver and Super Megaforce Pink and a blue key. It is not known what the blue key is yet. Silver and Pink look translucent.
Also present was the Turbo Falcon Megazord, Q-Rex Megazord, Super Mega Cannon, Legendary Morpher, MMPR Set B Set and Jungle Fury Set in packaging. Ninja Storm Blue, Red Dino Thunder, and Black Dino Thunder Keys loose. Also unidentified Red, Yellow and Pink keys were loose.