First off, I know this editorial isn't going to be great. Judge me or delete it if you want.
I recently watched the Avengers and there was a scene in the very beginning that I feel like may be overlooked. When Nick fury goes in front of the "counsel", it is mentioned that Phase 2 isn't ready and that they are forced to go into the Avengers initiative.
Most people think that Tony will create Ultron, but what if it is this counsel and shield that creates him. What if he's been being built this whole time?
With the first trailer for Winter Soldier out today, it's obvious that shield can't be trusted and want to "take care of threats before they happen". All signs point to this being the plan all along