For some there seems to be a debate as to whether they’re going in a Grey direction with the ST and to me there is no doubt as to where they’re going with this:

“First comes the day
Then comes the night.
After the darkness
Shines through the light.
The difference, they say,
Is only made right
By the resolving of gray
Through refined Jedi sight.”
― Journal of the Whills, 7:477

“All hail the light, the Dark, and they Gray”
― Excerpt from Empire’s End

“Light, darkness, the balance.”
― Rey

“It’s so much bigger.”
― Luke Skywalker

“And as a lot of people know, it’s difficult when you meet your heroes because it might not be what you expect.”
― Daisy Ridley

This and having characters like Bendu come into canon makes the evidence overwhelming in my opinion. Though it’s possible Luke’s line could be in reference to something even bigger than Ashla, Bogan and a balance between the two but as far as I’m concerned Luke will be either a Grey Jedi or a new Force Wielder that has seen the benefits of balance between the Light and Dark Sides of The Force or the need to use your anger, fear and aggression at certain times.