Well since the two parter finally aired, we can now finally discuss something about this interesting new villain named Queen Chrysalis and her own race the Changelings. It's now proven that their intention in taking over Equestria is explained by their source of nourishment being true love, and that Equestria has "more love than [they] have ever encountered." But....I wonder myself what's the cause of this?
Well this is my own headcanon so....this isn't official, but you can tell me if this contradicts the canon of the cartoon.
The Changelings may have appeared thousands of years ago in Equestria before Discord wreck havoc and the Elements were discovered. They somehow terrorized the whole land, feeding on the love of people while at the same time killing each and every pony that isn't their own kind, to the point that it wiped out half of the Population of Equestria. I guess that time Celestia's and Luna's parents were still alive and both princesses were still foals.
So I could bet this: Probably the King and Queen of Equestria go on a all-out war against the Changelings and defended the whole kingdom, until Queen Chrysalis appeared and goes berserk on them. Well the royalty did fight back but on that time, she is pretty much God-Like and totally dominated the battlefield, killing a lot of soldiers serving the royal family and also killing a lot more ponies on her wake. Her somewhat God-like powers pose a threat to the kingdom and the only way to defeat her and Changelings......is through the Power of the Elements.
The Elements of Harmony were created and then used against her, This time stripping off some of her powers and sentencing her and the Changelings into Eternal Prison, banishing her into the farthest region of Equestria. But the bad side before she was sealed, she killed both the king and queen and died. And with their roles as rulers being passed to the Princesses, they will uphold that duty to make sure no evil could touch Equestria.
But the barrier that holds the Queen and her minions grows weaker after the years and she broke free, but she doesn't regain all of her powers. Instead she kidnapped Princess Cadance and throw her to the mines of Canterlot while she took her place so she can drain of Shining Armor's love energy, regaining her God-Like Strength.
If the ending is different, she would have killed the mane 6 and the princesses, and also killing Princess Cadance and destroying the Elements. And then she wiped out the whole Pony Population with her God-Like Powers for her minions to claim. GAME OVER.
That is my headcanon IF they didn't stop her. But yeah.......she could cause more bloodshed in Season 3.