Ash promises Zorua at the end that he'll visit Zorua's homeland next on his journey. He follows through by visiting the Unova region right after the events of this movie, in the television show.
As of this movie, Ash has seen all the Legendary Pokemon from the first four generations at least once.
The teaser trailer shown at the end of Pokémon: Arceus and the Jewel of Life (2009) showed Ho-Oh and Lugia locked in an aerial battle, while a later trailer showed Zoroark changing into an illusion of Ash--a much darker version of Ash. This is from an abandoned plot that had Zoroark working alongside Kodai instead of being under his control. Ultimately, none of these elements made it into the final movie.
This movie marks the first time all three of the Legendary beasts appear at the same time in the anime, and also the first time Raikou receives a starring role in a movie. This movie also marks the first time a Shiny Legendary Pokemon (in this case, Raikou, Entei, and Suicune) appears in the anime.
This is the third movie so far that does not have a Legendary Pokemon as the main featured Pokemon, the first being Pokémon 3 the Movie: Spell of the Unown (2000) and the second being Pokémon: Lucario and the Mystery of Mew (2005).