The Japanese Opening 2 for XY has revealed some spoilers such as:
1. First of all, all the mega Pokemon at the beginning, and the many Mega Stones, one of them especially, like right there in your face.
2. Korrina is reading her book next to her Lucario, which is sleeping (I think)
3. Shauna, Tierno, and Trevor are shown. Shauna has a Bulbasaur, Tierno with a Squirtle, and Trevor with a Charmander.
4. Ash's Fletchling evolves into a Fletchinder, and he also has a Hawlucha.
5. The Champion is seen with her Gardevoir, battling Ash and Mega Evolving it.
6. Ash is seen battling Korrina with her Mega Lucario.
7. A trainer is seen with a Mawile, another seen with a Lucario, and then the Champion along with her Gardevoir.
8. At the end, Korrina and Lucario are seen running toward the group, Korrina's arms wide open.
The opening is here: