From CoroCoro and Pokémon Sunday,
Here are the news:

1) Red Gyarados remains at the Lake of Rage and is at level 30.
It appears that it will be raining when it is encountered.
2) When Surfing, you appear with the icon of standard Surfing like DPPt.
3) Eusine from Crystal appears in the story based on the Legendary Beasts.
4) Nine games that utilize the touch screen of the Nintendo DS will be in the game.
-One of them is named Pokéathlon, there is a special building in Goldenrod City.
5)
a) Ho-Oh (HG/Tin Tower) and Lugia (SS/Whirl Islands) will be level 45.
b) They will be Level 70 in opposite games.
artwork of the Pokémon Entei, Raikou and Suicune, as well as Eusine.
7) Entei, Raikou and Suicune will roam Johto at Level 40.
8) Overworld sprites of the said Pokémon in the Brass Tower can also be seen.
9) Part of Lugia's sprite can also be seen.
10) The Kimono Girls will have roles in the storyline and will be met several times.
11) Legendaries Pokémon: Mewtwo in Cerulean Cave, Latios (HeartGold) and Latias (SoulSilver) roaming Kanto.