Okay, rather than just editing the last post over and over again, I'm going to start a new post on the latest Mega Evolution news from X and Y. Anyway, there's recently been a new video that showcases the new Mega Evolutions in the games, and reveals a couple other details. Take a look.

So this video pretty much confirms details that we already know. One is that these new forms are going to be called Mega Evolutions (which is why I'm no longer putting the term in quotes). It also confirms that these evolutions can only be triggered while the Pokemon is holding a Mega Stone. One new detail that this video reveals is that the stone used for Blaziken's evolution is only available through a special event. Which makes sense when one considers that Blaziken is a fully evolved Starter Pokemon from another region. According to a news update on the Anime News Network (ANN), the other Mega Stones are supposedly found throughout the Kalos Region.

Some more details that were revealed (and I admittedly forgot to post about this info before), are more of the changes that these Mega Evolutions cause besides the dramatic change in appearance.

• Mega Mewtwo: Gains the Ability: Insomnia
• Mega Blaziken: Gains the Ability: Speed Boost
• Mega Lucario: Gains a boosted Attack Stat and the Ability: Adaptability
• Mega Mawile: Becomes a Steel/Fairy-type and gains Defense and Special Defense Stat boosts, along with the Ability: Huge Power
• Mega Absol: Gains a boosted Attack Stat and the Ability: Magic Bounce
• Mega Ampharos: Becomes and Electric/Dragon-type and gains the Ability: Mold Breaker
• Mega Kangaskhan: Gains the Ability: Parental Bond, allowing mother and child to fight as a team

This was all on the Serebii,net page on Mega Evolutions, but I thought I'd post it here too. Anyway, that's all of the details known at the moment. Though there does seem to be a few specific details that are still unknown. I'll update as soon as I learn more, so stay tuned.