with all the leaks, this quote makes total sense

Okay… what is Discord eating? Anyone know?

@Ping_chan
 
You actually bring something up. Shouldn’t Discord have been able to sense Tirek stealing all the earth ponies’ magic?

He knows Grogar is present. He also knows he needs Twilight to defeat him. Cuz friendship always prevails and stuff.

@Beau Skunky  
Would Discord be able to truly enjoy chaos if he always knew what was about to happen?

Coming from Discord, this is a huge compliment.
 
As for the speculation, I don’t think he’s omnipresent, (after all, he didn’t foresee Tirek betraying him, and such) I think he just assumes there’s something coming, as he’s kinda pessimistic, and as stated can sense magical imbalances. So he might have some foresight, but doesn’t know exactly what’s going to happen.

Your sarcasm is very reassuring, Discord.

Discord has faith in you, Twily.

I think it should be noted that the very first thing you see when the scene changes, after he says this is Grogar, right before Cozy Glow zooms into frame. I think that’s an implication he’s still the ultimate threat, after all.
 
It’s like how Cozy Glow opened the door immediately after when Rarity asked how Flim and Flam could’ve gotten the book, at the ending of Friendship University.
 
(Oh, and considering how Discord can sense magical imbalances, it’s entirely unsurprising if he knew those three were there the whole time. To be fair to Tirek though, I don’t think Discord ever told him that he could do that)

Yeah, he knows

Of course he knows…

Well that’s not foreboding at all.