Remember that if the emotional instability in the magic available to the ponies has to be removed, it means that the Mane 5 may have to jump into the mysterious ancient times from the time before Equestria existed, perhaps even before the ponies’ federated society divided between earth ponies, the pegasi and the unicorns originated. For the latest news from IDW, it seems that Discord in his escape has become a storyteller who can be of great help when the Mane 5 needs to learn about the past.
There are so many questions from the past of the G4 that have never been answered, such as how the Everfree forest originated and why a lot of dark and dangerous magic was there or nearby. We do not know where the windigos came from and why they would exterminate the Ponykind. We also do not know how the alicorns originated, or why they stood out from other ponies, and assume the role of shepherds of the Ponykind.
And the important question will be when the magic came to the ponies for the first time. This may be what the G5 will be about in the future, not just the G4 - but the background of the whole world as a magical world will be explored. Sunny has an advantage that Twilight does not have, by growing up in a magic free world, she has the ability to be able to look at things from the outside, such as when studying magic. She was too gullible in the face of magic at first, but she’s learning.