Inside sources claim that we're not just getting one or two new types, we're getting FIVE. Here's what we're dealing with now:
SOUND: Finally becoming its own full-fledged type, several older Pokemon are getting reclassified with this secondary typing (For instance, Jigglypuff is now Normal/Sound). It seems to be strong against Rock Types.
LIGHT: You heard that right. It's supposed to represent light and the color spectrum (i.e., rainbows). Xerneas is partially.of this type. Absol is re-typed as Dark/Light.
SHADOW: After having been toyed with in Colosseum, the Type is back in full force. It seems all of the moves from XD are back. The idea is to make a truly 'evil' kind of Pokemon. Yveltal is partially of this Type.
TOXIC: Now considered to be separate from Poison (which drops defense every turn), it seems to be good against Water enemies.
NO TYPE: As in, no weaknesses, resistances, or immunities, but none of its moves are super-effective. Based around a strange alien-invasion storyline that's seen in the post-game. Only one Pokemon has this type, and it rivals Arceus in power.
Classic Mode turns off the new types, but it must be unlocked after beating the Elite Four. Easy Mode and Challenge Mode are available from the start.
Another new thing they're adding are Pokemon 'Traits', which is a bonus given to attacks not of the Pokemon's type (For instance, Charizard has Dragon-like Traits). A few Pokemon have different Traits depending on form. Most Unown have different Traits depending on letter.
Friendship is being played up heavily, as a new command has been added in battle that acts as a last resort button. You are given the option now of deleting your fifth move or saving it in your Final Option box. When your last Pokemon is down to half health, they will be allowed to use this move, which gets stronger through friendship. If you get the health back, you lose the option.
Also, the starters' final forms are Grass/Rock, Water/Flying, and Fire/Fighting.