Yeah well, Avengers is now 11th with a billion dollars. It's going to be number 3 before next weekend at this pace.
I was thinking about this possibility as well. Coulson didn't really strike me as anything but an utterly disposable character, but he seems to have gained sufficient traction to perhaps warrant a return.And for Vision-- he is someone with memories of someone else - that could be how Coulson comes back.
As for possible new Avengers - personally I've always disliked Pym and Janet, so if they never show up I don't mind. Stark could built Ultron. And for Vision-- he is someone with memories of someone else - that could be how Coulson comes back.