So nothing from EG is canon right?
I really don't want relationship stuff in the main story.
it depends. they might mention the adventure happened, or vaguely note "remember when i went to that strange world?", or perhaps absolutely nothing at all.
based on what i've gathered, what goes on is similar to a typical pony episode. hardly any continuity.
the Flash/Twilight relationship has been described as minor and completely ignorable thus far, so i wouldn't worry about it
and Kakashi is supposedly going to see it tomorrow, so we can bug him for details afterward