Phase four Our age has not so much redefined irony, as focused on just one of its aspects. Irony has been manipulated to echo postmodernism. The postmodern, in art, architecture, literature, film, all that, is exclusively self-referential - its core implication is that art is used up, so it constantly recycles and quotes itself. Its entirely self-conscious stance precludes sincerity, sentiment, emoting of any kind, and thus has to rule out the existence of ultimate truth or moral certainty. Irony, in this context, is not there to lance a boil of duplicity, but rather to undermine sincerity altogether, to beggar the mere possibility of a meaningful moral position. In this sense it is, indeed, indivisible from cynicism.
The end of irony would be a disaster for the world - bad things will always occur, and those at fault will always attempt to cover them up with emotional and overblown language. If their opponents have to emote back at them, you're basically looking at a battle of wills, and the winner will be the person who can beat their breast the hardest without getting embarrassed. Irony allows you to launch a challenge without being dragged into this orbit of self-regarding sentiment that you get from Tony Blair, say, when he talks about "fighting for what's right". Irony can deflate a windbag in the way that very little else can.