I think one thing that needs to happen is Bungie/Acti announcing that some new free DLC areas will come and to lay out what they will be and when they will come. It's very unlikely, I know, but I think it would bring some goodwill back in peoples' minds. There's just not enough content, and I can't help but think that realistically the only CHANCES of new areas will be in the expansion packs (if, even then. The first one is supposed to take place on the moon, and that's not exactly the most environmentally diverse place).
the first two DLC packs were part of the limited edition version so they're not going to give those away.
I don't think people will stick around long enough to see a third.