I think I figured it out. I want to make a note here, when you're a writer and you study writing, literature, and all the formulas used over time you start to see how they keep repeating themselves over and over again. It is fun when you get thrown for a loop though when you don't realize where a story is going.
I came to a realization though that each character has been receiving different items that each give off a rainbow shimmer. I perceive that these items are the keys for the chest that was shown after episode 1 of Season 4, but why? To recap...
Rarity receives a spool of rainbow colored wool from a character named Coco.
Rainbow Dash receives a Wonderbolt badge from Spitfire.
Pinkie Pie receives the rubber chicken "Boneless" from Cheese Sandwich.
Fluttershy receives a flower from Seabreeze the leader of the Breezies.
Applejack receives a single coin from Silver Shill.
Why is each item important? Well before the climax and conclusion of each episode, a rainbow appears and a glimmering rainbow shines in the character's eyes. Each character so far has remembered their Element of Harmony, because the Elements of Harmony were used on the Tree of Harmony. Since they have received these items by not only remembering their element, but the true meaning of their element. I presume that they become keys. Think about it... Rarity finds out the true meaning of generosity, Rainbow Dash finds out the true meaning of loyalty, Pinkie Pie finds out the true meaning of laughter, Fluttershy finds out the true meaning of kindness, and Applejack finds out the true meaning of honesty.
Now all that we need is for Twilight to get her key and find out the true meaning of magic. Wonder how that will turn out.