I sort of read it like this:
... It looks like the release date might be May 1, 2015, but that can change depending on people's schedules. The beauty of 'The Avengers' is that you've got so many people in this that even during the shoot if someone has to do another film they can just focus on [other characters]."
Not that those are the most credible of sources either. This insider has no clue because Marvel contracts would certainly outweigh any other commitments for the major actors/characters so scheduling conflicts have little to do with it. But if there is another Marvel movie that Disney wants to release that summer, Avengers 2 will be in July. Right now there is nothing currently scheduled, but that can change.