Above is a screenshot from the U.K. home video release of the Avengers. You may note a small difference, in that Agent Coulson no longer has a chunk of Loki's staff protruding from his chest, although it's clearly still going into his back.
What does this mean for our beloved Agent of SHIELD? Absolutely nothing. I don't know why this scene was edited for the U.K. release, but the fact it wasn't edited for other countries means it has absolutely no ramifications as to whether Coulson survived or not, as much as I wish they did. As plenty people have pointed out before, Marvel and Joss Whedon have plenty of reasonable ways to bring Coulson back in they want to; if they felt this scene needed to be altered for some kind of character reason, they would have changed it in all home video releases, not just the U.K.'s. If you see anyone implying this has any kind of relevance other than 1) the U.K. had a censorship issue or 2) someone made a booboo remastering that scene, pay them no attention whatsoever. And this comes from someone who would happily kill any 20 of you to bring Agent Coulson back for the SHIELD show.