Lorewise, i don't think Jitte (because for Kaladeshians, who's Umezawa?) would happen... Same for phyrexian and Ashnod's altar.
The Chain Veil would be strange to happen because it is a cursed magical item that is unique (Legendary).
IMO, Chalice of the Void is almost certain. Oblivion Stone is a good call, but not certain.
(s)he is not in the OGW set, and that is certain, because of the name/number crunch (eldrazi mimic is 2 and endbringer is 3), unless emrakul is not being called by it's name, wich is almost impossible given it's a character in magic story.... My hint is Innistrad! because of the distorted cross in the teaser. Actually, can Emrakul distort thing too?
The Chain Veil would be strange to happen because it is a cursed magical item that is unique (Legendary).
IMO, Chalice of the Void is almost certain.
Oblivion Stone is a good call, but not certain.
Some possibilities...
Spellskite
engineered explosives
Staff of Domination
Trinisphere
Damping Matrix
vedalken shackles
Batterskull
Sensei's Divining Top would be awesome, but a little lore-forced too
howling mine and winter orb would be meh, but are possibilities, too.
And probably there will be a 5 card cycle from AER