Hello /vp/, I know you guys are gonna be doubtful, but I work for Gamefreak.
I'm very, very low in the company, but I managed to find out what this whole ''Scoop of the Century" is.

No Pokémon evolve through levels anymore, they all have some alternative method. As you could guess, a lot of them evolve through enough play in Pokémon-Aime. There are many that work as Glaceon and Leafeon do, and require you to level it up under certain conditions (Being location, weather condition, etc). There is even a Pokémon that only evolves if you level it up while poisoned.
There are two new Pokémon which evolve when fighting in a battle (Either against each other or side by side in a double battle).
Some old Pokémon now only evolve through O-Power related methods.
There are a handful of new trade evolutions, including one with a new Pokémon. This Pokémon splits off into two Pokémon when traded, the receiver gets the Pokemon's ''Spirit'' and the giver gets the empty shell of the Pokémon. This can be prevented by giving it an Everstone.

Your starter evolves by the use of items which are given to you throughout the story. The first item is received after you beat the 3rd gym. The second item is given to you by Serena or Calem (Depending on your gender) after you battle them at the end of Victory Road. After you beat the elite 4, Serena or Calem can be found in Vaniville Town and will evolve an unevolved starter for you, if it is at a certain level.

This was done to make the game feel more unique and immersive for everyone.