To Infinity Stones, and beyond. 

The Marvel Cinematic Universe is a fascinating beast. Phase One of the films were structured to build up to an Avengers movie. Phase Two was designed to reflect on the action of said Avengers movie and see how the individual heroes coped. Avengers: Age of Ultron dropped the bomb (after escorting all the civilians onto a hovercraft and blowing up the city in the air so the impact wouldn't affect surrounding areas) that Phase Three will be all about the Infinity Stones.