User blog comment:David McMartin Son Of Sparrow/Avengers 2 stuff/@comment-3569533-20140728010450

What Ive heard of the premise supposedly is this

With  S.H.I.E.L.D. destroyed and the  Avengers needing a break from stopping threats,  Tony Stark creates  Ultron, a self-aware, self-teaching, artificial intelligence, who can assess threats and control Stark's Iron Legion. However, things quickly go awry when Ultron decides that humans are the main enemy and sets out to eradicate them from Earth. [2]

Avengers tower is already built, if you blink you miss it in Captain America Winter Soldier *during targeting sequence)

Tom Hiddleston has said multiple times he's not doing the role this time, thought could be making it up to keep us all guessing 

'''Red Skull is a possibility, but what may be a secondary antagonist is Baron Von Strucker, who leads HYDRA now. (HEIL HYDRA btw)'''

'''Some of the other stuff you said is cool and I cant wait for this epic movie to come out and try and top the first movie. '''

Hulkbuster minor rumor we have seen a concept art though could just be that