Well, I'm an ex-boyfriend of a famous teacher Pokemon administrator of a group of facebook (related pic).

He has had inside information about what will be in the future demo that will be released in October. He made a point of saying that only China has information about the full game, then it is quite possible that only the "chinese leak" is real.

In the demo we can get to the first gym (or captain, you name it, it's the same shit) but evolve all pokemons to their last forms, including initials.

He also said that the final forms will not be the owl archer, wrestler tiger and furry mermaid, at least not exactly like those leaked designs. The second stage Litten is a bipedal creature, though. :(

Mega Evolutions will be in the game and initials of past generations receive new Megas. Every major opponent during the game will have a pokemon able to evolve mega (mega probably evolve in rematchs). In the demo we face three major trainers (one captain, a kahuna and rival) and two of them give you Mega Stones, including a Greninjite (he chose Litten as initial, then probably received a Mega Stone Pokemon of the opposite type).

During the demo there was no way we could ride on a pokemon, but an NPC in the second city asks for a side quest to help you take care of your herd of Tauros. When we finished it does not give us anything, but asks to come back when you need some help. It may be the sign of something.

That was more relevant than the demo brought and what I was expecting more to know. I hope it fill your heart.