Stark isn't creating Ultron. No way. I personally think he has already been created. We start seeing him soon. As an AI. I don't think he will be created then defeated in avengers 2. I think he'll be slightly built up till avengers 2, as we find out what he wants, and why he exists. Then in antman we find out his origin. There'd be no point to pym.
I think that teaser was just revealing ultron, and how he manipulated a damaged man, or damaged a man to the point where he took over. Or they just used his helmet cause it'd be a cool effect...it can be seen where Ultron got personal with tony, To the point where hey, what if Ultron was this AI that was created and defeated by pym, but it still existed, without a body though, and has been waiting for the right chance/opportunity to take the world?
Little theory that some type of AI was being used by Mandarin, to control his soldiers, and the suits, hell, the interior of the iron patriot, the HUD was different, a different color, which made me think, different AI..Ultron couldd have fallen into that, and he sort of aligned himself with the Mandarin, through Ultron's somewhat influences, the events of Ironman 3 were caused by him. Stark, the only other man who seems to have a high tech AI. He manipulates things completely to the point where this man no longer has any ironman suits, not to mention, left him mentally unstable. Ultron slowly becomes more and more prominent through the show, and in Cap 2. By Avengers 2, we know this AI exists, and what it wants. and, there it is
that's what I think, well, what I would imagine be a way to do it.