I don't think it will be the end, but you never know.
There always are new characters popping into MLP to pull the plot further, so new villains appearing in the human world wouldn't surprise me.
By the way, I liked the idea with Sunset wanting to get back to Equestria. =3
I really like Equestria Girls series, so I'd gladly see it going further.
The first movie brought me to MLP, so it has a value for me.
Besides plot holes and irrational things, I love these movies! =3
Though I was completely disappointed by Friendship Games, I hope this one (and the future ones) will be much better!