i think he probably has to be the next one. maybe they run it where after the kang battle they all get destroyed but one or maybe they just all disappear or something, but i think it will be the very next one. i could be wrong though, since they have yet to come back to loki after the masters of evil episode. maybe they have loki take him over or something.

He's coming, but I love how the brought him in, I like the feeling you get as you watch Hank "teach" Ultron the concept of violence, you get that dark feeling that only makes you know this isn't going to end well, plus Ultron reminds me of the robots from iRobot.
 
I'm just excited about all of revelations this show has, Marvel really outdid themselves this time, the whole show from the villains appearing and the Avengers working together as a group, seeing them cave under the pressure and seeing others shine when the time comes, it's simple EPIC!