In an interview with Junichi Masuda this was said (I suck at starting stories.)
1. Pokémon gain experience even when the opposing wild Pokémon is caught. (This was stated in another interview.)
2. Sky Battles are limited to Flying-type Pokémon and those with the Levitate ability (as previously confirmed). Some moves can’t be used.
3. There is an adjustment to the inheritence system of breeding.
4. Ghost-type Pokemon can freely escape from battle without being influenced by Shadow Tag. (The official website mentioned trapping moves.)
5. The item Exp.Share will revert to Exp.All as in Generation I, where when one Pokémon holding this item participates in battle, all other Pokémon in the team receive experience as well. Unlike in Generation I, the experience is not split but rather received by all Pokémon. This means that the participating Pokemon receive 100% experience, while non-participating Pokémon receive 50% experience.
6. When distributing new moves and abilities, priority was given to new Pokémon.
7. The CGI style is different from that of Pokémon Stadium and Pokémon Battle Revolution, because those games were supposed to emulate “realism within fantasy”. Since the handheld Pokémon series is supposed to be accessible to everyone, battles were made “cuter”.
8. The standard selection process for Pokémon to be Mega-Evolvable is based on three points: visual looks, popularity and game balance.
9. The power-up of Mega-Evolved Pokemon is meant to elevate them to the class of legendary Pokémon, hence the restriction of only one Pokémon being allowed to hold a Mega Stone during battles.
10. The timing to Mega-Evolve is selectable.