I'm guessing late October/early November before we get the rest of the season. The Discord two-parter was scripted, animated and voiced during season one's production, so it was thrown up early as a means to drum up interest in the new season. Stupid bastards getting our hopes up...
I know I'm probably the only one who thinks like this, but after the scene with Celestia, I'm not getting much of a Q vibe with Discord. He actually reminds me of AM from the game version of
I Have No Mouth And I Must Scream. He separates the heroes into different mazes, while using their own personality flaws against them to prove that
Ponies Are Bastards. He gleefully twists the rules to fit his own desires, and becomes far more direct (as with Fluttershy) when things start going against him. Just listen to what Celestia says about him, or look at what he does to the mane six. He's not a trickster; he's
flat fucking evil.
WILDLY STUPID WMG AHEAD:

Hell, I'd go as far to say that's his whole plan. He doesn't just want to take over Equestria again; he wants to prove Celestia and Luna wrong, that the ponies they love so much are just a bunch of bastards like him. His fatal mistake was not corrupting Twilight; her own stubborn nature, relationship with Celestia, and studies on friendship give her enough to remind her friends who they really are, and this breaks the corruption. When Discord sees this, he tries to
Mind Rape the cast again, but this time their better natures show through. Their friendship turns out to be the "where it all began" from the riddle, the actual Elements of Harmony reappear, and Discord is either turned back to stone or destroyed once and for all.