In 2016, the opening episode for Friendship is Magic Season 6 will very likely be a two-parter as is usual for MLP seasons.

Almost certainly, the episode will involve the birth of Princess Cadance's baby pony, and Shining Armor and the Mane Six, of course, will appear.

I suspect the two parts of the episode will take place within the Crystal Empire, and will involve an enemy like King Sombra or Lord Tirek or the Changelings under their Queen Chrysalis.

A possible additional bonus: Fluttershy's brother will make his debut, as Andrea Libman mentioned him in July 2015 at the San Diego Comic Con.